diff --git a/js-assembler/assemble-open-coded.rkt b/js-assembler/assemble-open-coded.rkt
index a9f3b4f..b0eb98f 100644
--- a/js-assembler/assemble-open-coded.rkt
+++ b/js-assembler/assemble-open-coded.rkt
@@ -81,10 +81,11 @@
              (format "RT.checkedNumEqualsSlowPath(M, [~a])" (string-join operands ","))])]
           
           [(>)
-           (format "RT.checkedGreaterThan(M, ~a)"
-                   (string-join operands ","))
-           ;; (assemble-boolean-chain "plt.baselib.numbers.greaterThan" checked-operands)
-           ]
+           (cond
+            [(< (length operands) MAX-JAVASCRIPT-ARGS-AT-ONCE)
+             (format "RT.checkedGreaterThan(M, ~a)" (string-join operands ","))]
+            [else
+             (format "RT.checkedGreaterThanSlowPath(M, [~a])" (string-join operands ","))])]
           
           [(>=)
            (assemble-boolean-chain "plt.baselib.numbers.greaterThanOrEqual" checked-operands)]
diff --git a/js-assembler/runtime-src/baselib-check.js b/js-assembler/runtime-src/baselib-check.js
index 64e4c32..44ed920 100644
--- a/js-assembler/runtime-src/baselib-check.js
+++ b/js-assembler/runtime-src/baselib-check.js
@@ -51,27 +51,6 @@
         };
     };
 
-    var makeCheckParameterizedArgumentType = function (parameterizedPredicate, 
-                                                       parameterizedPredicateName) {
-        return function (MACHINE, callerName, position) {
-            var args = [], i;
-            for (i = 3; i < arguments.length; i++) {
-                args.push(arguments[i]);
-            }
-            return testArgument(
-                MACHINE,
-                function () { return parameterizedPredicateName.apply(null, args); },
-                function (x) {
-                    return parameterizedPredicate.apply(null, [x].concat(args));
-                },
-                MACHINE.e[MACHINE.e.length - 1 - position],
-                position,
-                callerName);
-        };
-    };
-
-
-
 
 
     var makeCheckListofArgumentType = function (predicate, predicateName) {
@@ -172,15 +151,36 @@
         baselib.bytes.isBytes,
         'bytes');
 
-    var checkNaturalInRange = makeCheckParameterizedArgumentType(
-        function (x, a, b) {
-            if (! baselib.numbers.isNatural(x)) { return false; }
-            return (baselib.numbers.lessThanOrEqual(a, x) &&
-                    baselib.numbers.lessThan(x, b));
-        },
-        function (a, b) {
-            return baselib.format.format('natural between ~a and ~a', [a, b]);
-        });
+    var checkNaturalInRange = function(M, callerName, index, a, b) {
+        var expectedTypeName;
+        var x = M.e[M.e.length - 1 - index];
+        // fast path: if a, b, and x are numbers
+        if (typeof(x) === 'number' && typeof(a) === 'number' && typeof(b) === 'number') {
+            if (a <= x && x < b) { 
+                return x; 
+            }
+            else {
+                expectedTypeName = baselib.format.format('natural between ~a and ~a', [a, b]);
+                return baselib.exceptions.raiseArgumentTypeError(m, 
+                                                                 callerName,
+                                                                 expectedTypeName,
+                                                                 index,
+                                                                 x);
+            }
+        } else {
+            if (baselib.numbers.lessThanOrEqual(a, x) && baselib.numbers.lessThan(x, b)) {
+                return x;
+            } else {
+                expectedTypeName = baselib.format.format('natural between ~a and ~a', [a, b]);
+                return baselib.exceptions.raiseArgumentTypeError(m, 
+                                                                 callerName,
+                                                                 expectedTypeName,
+                                                                 index,
+                                                                 x);
+            }
+        }
+    };
+
 
     var checkInteger = makeCheckArgumentType(
         baselib.numbers.isInteger,
@@ -271,7 +271,6 @@
     exports.testArgument = testArgument;
     exports.testArity = testArity;
     exports.makeCheckArgumentType = makeCheckArgumentType;
-    exports.makeCheckParameterizedArgumentType = makeCheckParameterizedArgumentType;
     exports.makeCheckListofArgumentType = makeCheckListofArgumentType;
     exports.checkOutputPort = checkOutputPort;
     exports.checkInputPort = checkInputPort;
diff --git a/js-assembler/runtime-src/runtime.js b/js-assembler/runtime-src/runtime.js
index c5c3c37..9168767 100644
--- a/js-assembler/runtime-src/runtime.js
+++ b/js-assembler/runtime-src/runtime.js
@@ -834,12 +834,10 @@
     };
 
     var checkedAdd = function(M, x, y) {
-        var i;
         var sum;
         // fast path optimization: binop addition on fixnums
         if (arguments.length === 3) {
-            if (typeof(x) === 'number' &&
-                typeof(y) === 'number') {
+            if (typeof(x) === 'number' && typeof(y) === 'number') {
                 sum = x + y;
                 if (sum < -9e15 || sum > 9e15) {
                     return checkedAddSlowPath(M, Array.prototype.slice.call(arguments, 1));
@@ -847,19 +845,7 @@
                 return sum;
             }
         }
-
-        sum = 0;
-        for (i = 1; i < arguments.length; i++) {
-            if (typeof(arguments[i]) === 'number') {
-                sum += arguments[i];
-                if (sum < -9e15 || sum > 9e15) {
-                    return checkedAddSlowPath(M, Array.prototype.slice.call(arguments, 1));
-                }
-            } else {
-                return checkedAddSlowPath(M, Array.prototype.slice.call(arguments, 1));
-            }
-        }
-        return sum;
+        return checkedAddSlowPath(M, Array.prototype.slice.call(arguments, 1));
     };
 
     var checkedAddSlowPath = function(M, args) {
@@ -874,24 +860,20 @@
         return sum;
     };
 
-    var checkedSub = function(M) {
+    var checkedSub = function(M, x, y) {
         // Assumption: at least two arguments to subtract.
-        var i;
-        if (typeof(arguments[1]) !== 'number') {
-            return checkedSubSlowPath(M, Array.prototype.slice.call(arguments, 1));
-        }
-        var sum = arguments[1];
-        for (i = 2; i < arguments.length; i++) {
-            if (typeof(arguments[i]) === 'number') {
-                sum -= arguments[i];
+        var sum;
+        // fast path optimization: binop subtraction on fixnums
+        if (arguments.length === 3) {
+            if (typeof(x) === 'number' && typeof(y) === 'number') {
+                sum = x - y;
                 if (sum < -9e15 || sum > 9e15) {
                     return checkedSubSlowPath(M, Array.prototype.slice.call(arguments, 1));
                 }
-            } else {
-                return checkedSubSlowPath(M, Array.prototype.slice.call(arguments, 1));
+                return sum;
             }
         }
-        return sum;
+        return checkedSubSlowPath(M, Array.prototype.slice.call(arguments, 1));
     };
 
     var checkedSubSlowPath = function(M, args) {
@@ -917,27 +899,35 @@
                 return x > y;
             }
         }
+        return checkedGreaterThanSlowPath(M, Array.prototype.slice.call(arguments, 1));
+    };
 
-        // Slow path.
-        if (! isNumber(arguments[1])) {
-            raiseArgumentTypeError(M, '>', 'number', 0, arguments[1]);
+    var checkedGreaterThanSlowPath = function(M, args) {
+        if (! isNumber(args[0])) {
+            raiseArgumentTypeError(M, '>', 'number', 0, args[0]);
         }
-
-        for (i = 2; i < arguments.length ; i++) {
-            if (! isNumber(arguments[i])) {
-                raiseArgumentTypeError(M, '>', 'number', i-1, arguments[i]);
+        for (i = 1; i < args.length ; i++) {
+            if (! isNumber(args[i])) {
+                raiseArgumentTypeError(M, '>', 'number', i, args[i]);
             }
-            if (! plt.baselib.numbers.greaterThan(arguments[i-1],
-                                                  arugments[i])) {
+            if (! plt.baselib.numbers.greaterThan(args[i-1], args[i])) {
                 return false;
             }
         }
         return true;
     };
 
-    var checkedNumEquals = function(M) {
+
+    var checkedNumEquals = function(M, x, y) {
         // Assumption: at least two arguments to compare
         var i;
+
+        // fast path optimization: binop comparison on fixnums
+        if (arguments.length === 3) {
+            if (typeof(x) === 'number' && typeof(y) === 'number') {
+                return x === y;
+            }
+        }
         if (typeof(arguments[1]) !== 'number') {
             return checkedNumEqualsSlowPath(M, Array.prototype.slice.call(arguments, 1));
         }
@@ -1126,6 +1116,7 @@
     exports['checkedNumEquals'] = checkedNumEquals;
     exports['checkedNumEqualsSlowPath'] = checkedNumEqualsSlowPath;
     exports['checkedGreaterThan'] = checkedGreaterThan;
+    exports['checkedGreaterThanSlowPath'] = checkedGreaterThanSlowPath;
     exports['checkedCar'] = checkedCar;
     exports['checkedCdr'] = checkedCdr;
 }(this.plt, this.plt.baselib));
\ No newline at end of file