[IndySam]

Originally Posted by Tristan Lall

That's exactly why it's hazy, though: let's say I use a 0.19 in thick × 1.00 in tall strip of polycarbonate as the backing material, with several screws into the bumper plywood. Will it be strong enough across a 20 in span? My gut feeling is that under most gameplay, it would not break, or even deflect appreciably. But what if the team used (brittle) acrylic instead? Or if they turned the strip 90° to buttress the plywood? I don't think it makes much sense for inspectors to be trying to make that particular determination—it will just be their best guess, and it's ripe for debate that serves no useful purpose.
If your bumper plywood ever breaks, even with no backing (and especially with the aluminum angle depicted in Fig. 8-1), you're probably doing it wrong. And if you use high-quality hardwood marine plywood (as opposed to the regular softwood stuff), you could probably span over 30 in without any backing, and suffer no ill effects.

I just don't think it's valuable to add a specification here, given that it's one more thing for teams to worry about, one more thing that needs to be checked (consistently) at inspection, and is probably superfluous anyway, given moderately-well-constructed bumpers.

in 2007 we had 38" bumpers on the back of our robot only supported on the ends. They were constructed out of high quality plywood and they were snapped in half, twice.