Robot Frame and Bumper Clearance Holes

[FRC1379]

In the thread http://forums.usfirst.org/showthread.php?t=11389, the response indicates that it is allowable to drill clearance holes in the plywood backing of the bumper to accomodate boltheads or other protrusions that extend beyond the bumper perimeter. However this would appear to be in violation of R16 which states that "When in the PLAYING CONFIGURATION, no part of the ROBOT may extend outside the vertical projection of the BUMPER PERIMETER." Many teams use frame designs which are bolted together or have minor protrusions through the frame for shafts, bearings, bushings or other parts.

Do teams need to design their robots such that the bumper perimeter is a flat surface with no protrusions whatsoever or does the no protrusion beyond the bumper perimeter rule only apply to robot parts above the bumpers?

[GDC]

Limited protrusions (less than 1/2 inch in depth) through the BUMPER PERIMETER by small items (e.g. heads of fasteners, ends of shafts/axles, bearing shoulders, other items of less than 1 inch in cross-section.) will be permitted.