[Ianworld]

I'll second Andrew Blair's comments. I have never seen a piece of lexan actually fail outright. I've seen it get bent or deformed slightly. So unless you need structural rigidity out of it keep it very thin and you'll do fine.

One suggestion is to arc it over the part of your robot that you want to protect. The shape of the lexan will help it deflect and absorb blows. The bowed shape also makes it stiffer than if it was layed flat over a hole.