Update on the box mag: for the front support im thinking of using something like the weaver flip up sights to mount the mag on without using the screw to make it stay in place. Since they some rotation you can just slide it on then fold the base of the mag up into the magwell locking in place. It will provide up and down support and the magwell will keep it from sliding forward and coming loose. Should be easy to swap back and forth between the box and regular mags as well. Now i jjust need to figure out what materials to use and how to actually mold them to the shape i want.