[GaryVoshol]

I thought of another interpretation to your question. When you say your bolts are 8.5" center-to-center, are these bolts the ones you are using to connect the BUMPER to the ROBOT, the fasteners?

That's not what is meant by "supported" in <R07-K>. That rule is talking about the ROBOT parts behind your BUMPER, what most people think of as the frame. There can be no unsupported sections of plywood - no sections that don't touch the frame - greater than 8" long. As long as you don't have any gaps greater than 8" in your metal parts where the plywood touches, you should be OK. The other exception in <R07-K>, the 1/4" part of the rule, allows for vagarities of build - bolt heads sticking out, slightly bent metal or warped wood, etc.

Most teams use 2 or 3 fasteners per side to connect their BUMPERS to the ROBOT.