Frame design question

[RRLedford]

What if frame is seriously convex to the point where it is curves a pocket into itself, like an island atoll and having an opening on the wide side just larger than a ball? Would the bumper have to wrap both the outside and the inside "shore" of the "lagoon"? Could several balls be rolling around inside the lagoon area without being considered possessed, or having penetrated more than 3" into the frame zone? Would all the robot's H/W have to be built up ONLY within vertical space directly above the atoll shaped frame, or could some hardware protrude into the space above the lagoon? Why would there even need to be a bumper inside anyway, since no impact could ever happen there, and only "topologically" it is still the "outside" of the frame?
Kind of tricky getting a shooter concept to fit with this scheme for sure.

-RRLedford