Actually, while there are several rules covering bumpers, the GDC pro-actively took the step of addressing how these rules would affect design in
Team Update #2 published wayyy back in early January.
Look at the last page and you will see that no robot can have an opening greater than 26" across, and "long and narrow" robots are limited to 16" across. Time to take out the TIG and reduce the opening a bit... should be easy enough to do... but do I detect the frame narrowing towards the rear of the robot? That might be an area for bumper concern, too... hard to tell from this angle.
Jason