[EricH]

Originally Posted by GeeTwo

I don't know how you're reading the "blue box". It specifically allows non-horizontal bumpers, as long as they stay in the 2"-10" range.

There is no explicit requirement that BUMPERS be perfectly parallel to the floor, however the requirement that BUMPERS be constructed per Figure 4?8, the vertical cross-section, does implicitly mean that a BUMPER should not overtly deviate from this orientation.

Emphasis mine. The blue box specifically states that the bumpers are IMPLICITLY required to be as close as possible to horizontal. Not explicitly required to be one way is not the same as specifically allowed to be another way. You're not explicitly required to use any particular fabric on your bumper, but a particular fabric is specifically allowed by implication.