Robots are required to use Bumpers to protect all exterior vertices of the Frame Perimeter. For adequate protection, at least 8 in. of Bumper must be placed on each side of each exterior vertex (see Figure 4‑1, Figure 4‑2, and Figure 4‑3).
No where in that rule does it say frame perimeter. It also doesn't specify if its the vertex of the frame or bumpers.