I thought I knew the answer to this question, until I saw the following response on the Q&A today:
Q. Are the corners along the frame perimeter that are formed from an opening in one side of the frame (like the lower left-hand example in Figure 4-2) considered "outside corners" and, if so, require 8 in of bumper along the frame perimeter from those points?
2013-01-22 by FRC0069
A. Gaps in the ROBOT'S frame that do not create corners in the FRAME PERIMETER are not considered "outside corners" of the FRAME PERIMETER.
I can't think of a way of asking this question without getting the inevitable: "The purpose of this forum is to answer specific questions about specific Rules. We cannot comment absolutely on hypothetical situations..."
Can a robot have a cutout into one end (such as was common for the ball loaders last season) that would result in less than 8" of frame remaining on either side, if the additional 8" bumper requirement was added to the adjacent sides?