I had the same thought. If bolts can't hold your bumpers on, how will Velcro?
As for the projector, feel free to bring one, as I haven't seen anything in the rules to the contrary. Realize that you probably won't be allowed to project on stuff outside of your pit, and limiting the projection area to inside your pit usually means that you could be better off having a small TV or laptop sitting out showing whatever you want to have projected.
That being said, there are still some cool uses for projectors. 1730 uses a projector for their
pit banner.