Please check section 4.1.6 of the manual for bumper rules:
http://frc-manual.usfirst.org/viewItem/3#4
R03 also defines the frame perimeter wich is important to the bumpers.
Each year, many of the rules change a little bit or a whole bunch. The bumper rules have been around since 2005, with continuous refinement. In 2010, the FRC Game Design Commitee switched over to the Red/Blue configurations with numbers on them. Often there is a change in height from the ground and whether they must be continuous or may have gaps. It would seem that these changes are primarily dependent on the game pieces and how they want the game to play.
Bumpers can be a very frustrating part of the inspection process. There are a lot of detailed rules that must be followed. Often teams that have the most trouble are focusing their design at the limits of the rules. IE, if the bumper length mus be 8" from the corner, they make that segment 8". Unfortunately if the cut is slightly short, of the bumpers don't fit tightly, you can end up in a condition where your bumpers are only 7 3/4" from the corner of the frame perimeter, and thus non-compliant. My recommendation is that teams add a little margin to their design if they can.