OpenSCAD Parameters not passing to child module-calls

// Customizable OpenBuilds V-Slot Rails, Using 2D Extrusion and render() Command, Allowing Each Working Face to be Closed or Slotted

/* [General] */
// Height (Y) of Extrusion Profile End View
VRailHeight = 20;

// Width (X) of Extrusion Profile End View
VRailWidth = 20;

// Length (Z) of Extruded Part
VRailLength = 10;



// Begin Rendering

VRailVitamin(Slots=1);

// Define Modules

module VRailProfile() {
    /* [Profile] */
    VWCenter = VRailWidth / 2;
    VHCenter = VRailHeight / 2;

    // Define Profile
    difference() {
        square([VRailWidth, VRailHeight]);
        for (i=[1:1:3]) {
            translate ([VWCenter,VHCenter]) {
                translate([(VWCenter-0.5),(VHCenter-0.5)]) {
                    render() SquareFillets();
                };
                rotate([0,0,90*i]) {
                    translate([(VWCenter-0.5),(VHCenter-0.5)]) {
                        SquareFillets();
                    };
                };
            };
        };
        translate ([VWCenter,VHCenter]) {
            circle(2.1,$fn=15);
        };
        for (i=Slots) {
            translate ([VWCenter,VHCenter]) {
                rotate([0,0,90*i]) {
                    translate ([0,-VHCenter]) {
                        VSlot();
                    };
                };
            };
        };

    };


    // Define subModules
    module SquareFillets () {
        difference() {
            square(1);
            circle(0.5,$fn=15);
        };
    };

    module VSlot () {
        VSlotHalf();
        mirror([1,0]) VSlotHalf();

        module VSlotHalf() {
            polygon (points = [[0,-1],[0,6.31],[0.21,6.1],[2.839,6.1],[5.5,3.439],[5.5,1.8],[3.125,1.8],[3.125,1.455],[5.58,-1]]);
        };
    };
};

module VRailVitamin (VRailWidth=VRailWidth, VRailHeight=VRailHeight,Slots=[1,2,3,4]) { // This set of parameters was originally defined for VRailProfile(). Leaving it defined there and here while calling VRailVitamin with a Slots[] value does not pass the value, even if I add Slots to the VRailProfile() call below.
    linear_extrude(height=1, convexity=10) VRailProfile();
};

//EOD