[EricH]

The support structure for the bumpers will define the frame perimeter in that case. Your frame perimeter must be <=120".

Because there is frame perimeter there, you will have to put 8" of bumper on both sides of the corner thus formed. Or, in this case, 11.5" of bumper covering the opening (because 8" of bumper + 8" of bumper = 16"...on a 11.5" section of frame). Not a legal configuration to leave the gap open, sorry.