...never had a single marker light on our pop-up manufactured in 2005.5 (none of the high-end pop-up manufacturers that I know of (costing $22,000+) have them on their units either). Our roof-line is at 8-foot 2-inches (roof closed, of course). Camper width: 87.5 inches (I don't think that there are any truck campers made, pop-up or hard-side, that fit half ton to 1 ton trucks narrower than about 84~87 inches; with jacks off, ~81 inches).
I had to put reflector tape markers on front of cabover (and, on the 4 jacks) myself. My reasoning is: walkers and cyclists can see the camper jacks as they (and we) drive by them (and us)...I guess I'm just going a step further (ie. being proactive).
I, too, would like to see the DOT regs on this (both State DOT, and Federal DOT).