Wow! My current stay solution is described here. It is OK, but could be better, hence my poking around.

Optimization is obviously a complicated process that commonly yields many solutions. Rolling on the wheel in Helix is obviously good - you reuse the existing structure and are able to roll with not much pain over big obstacles. Originally I was put off by the tiny wheels barely sticking out of the rack for rolling the folded Brompton. However, after I got the side wheels mounted, see here, I think I have a winner. The folded bike became extremely versatile. I move over buildings, streets, stairs, elevators, etc. operating like people pulling suitcases and becoming indistinguishable from that crowd. My 2 side wheel are also minimod/bikegang, while the 4 other original.