[DonRotolo]

Nice work.

Consider making the thin strips that lead from the edges to the wheel axles a bit thicker, perhaps like a filled-in "X" or hourglass shape instead of an "I".

We used a similar system of 80/20 in 2009 and it worked out very well.

I also like the concept of using the strength and stiffness of the bumpers as a structural element. Some spots for mounting them would be wise.