[Al Skierkiewicz]

Stuff,
The protrusions language is meant to allow for bolt heads, welds, rivets, etc. Bearings are pushing that definition. However, the FRAME PERIMETER as determined by the string method may include the bearings and still be under 112", your OK. I would be more inclined to pass your bumper design if if had shallow holes where the bearings are located rather than one long slot. From your description, it sounds like one or two of the plys in a plywood backing would be compromised. That is pretty significant.