[Qbot2640]

A picture would help explain what you're talking about...but:

If your are talking about adding a recess to the wood backing that will surround a bolt head but will not change the shape of the soft part of the bumper, then I believe you will be ok. The rules do allow for bolt head protrusions.

If you are talking about cutting a section the whole way through your bumper (such that the pool noodle and cloth are also affected) then I believe this will be disallowed. In 2012 we had notches to allow our bridge pushing arms to come down far enough...there was more than the specified 8" on each side of the notch, never the less - we had to rebuild our bumpers before we passed inspection. Further, our team number was in the center and we didn't have any way to paint new numbers, so we had to re-manufacture the middle portion just to display the numbers. Point of the story - make it right before competition so you don't spend time fixing something when you should be playing practice matches.