Bumper Zone Alignment

[Matt C]

R22 BUMPERS must be located entirely within the BUMPER ZONE, which is the volume contained
between two virtual horizontal planes, 4 in. above the floor and 12 in. above the floor, in reference
to the ROBOT standing normally on a flat floor. BUMPERS do not have to be parallel to the floor.

Emphasis is mine, the bumpers don't even have to be parallel to the floor, they just have to exist, in the correct construction per the other bumper rules, between 4 and 12 inches from the ground.