There has been a lot of discussion about this, as well as two rule updates (6 and 7)
http://usfirst.org/roboticsprograms/...nt.aspx?id=450
Bolts in the BUMPER ZONE can stick out of the FRAME PERIMETER, and you can make small holes in the back of the bumpers to fit the bumpers over the bolts.
Bolts above or below the BUMPER ZONE can NOT stick out past the FRAME PERIMETER.