OpenSCAD drone arm holder and mount

function hypotenuse(a,b) = (a*a + b*b);
$fn=50;

//Size of drone
drone_size = 500;

//Length of cross arms in order to maintain square dimensions
cross_l = hypotenuse(drone_size,drone_size);

//Diameter of the rod, along with radius
rod_d = 15.8+0.2;
rod_r = rod_d/2;

//Thickness of the fitting the rods insert into
fit_th = 5;
fit_in_r = rod_r;   //Inner radius, same as rod that will insert
fit_in_d = fit_in_r * 2;    //Diameter
fit_out_r = rod_r + fit_th; //Outer radius, added thickness
fit_out_d = fit_out_r * 2; //Diameter

//Length of the fitting outward (aka radius)
fit_l = 50;
difference(){
    union(){
        translate([0,0,fit_in_r])
            cylinder(r=fit_l,h=fit_th);
        rotate([0,90,0])
            cross_fitting(fit_l,fit_in_d,fit_out_d,false);
    }

    translate([0,0,fit_out_r])
        union(){
        radial_hole_punch(fit_l/2,4,4.01,fit_out_d);
        radial_hole_punch(fit_l-fit_th*2,4,4.01,fit_out_d);
        radial_hole_punch(fit_l/2,4,8,fit_th/2);
        radial_hole_punch(fit_l-fit_th*2,4,8,fit_th/2);
        }
            translate([0,0,-fit_out_r])
            union(){
            rotate([0,180,0])
            radial_hole_punch(fit_l/2,4,8,fit_th/2);
            rotate([0,180,0])
            radial_hole_punch(fit_l-fit_th*2,4,8,fit_th/2);
            }
            translate([0,0,fit_out_r])
    rotate(45)
    radial_hole_punch(fit_l/2,4,4,fit_th);
}
module cross_fitting(r,in_d,out_d,through=false){
    difference(){
    //Create the base cross we'll cut out
        for(i=[0:4-1]){
                rotate([360/4*i,0,0])
                    cylinder(d=out_d,h=r);
            }

        for(i=[0:4-1]){
            rotate([360/4*i,0,0])
            if(through == true){
                cylinder(d=in_d,h=r+1);
            }else{
                translate([0,0,out_d/2])
                cylinder(d=in_d,h=r+1);
            }

        }
    }
}
module radial_hole_punch(r,holes,hole_d,depth){
    for(i=[0:holes-1]){
        rotate(360/holes*i)
            translate([r,0,0])
                mirror([0,0,1])
                cylinder(d=hole_d,h=depth);
    }
}