The trash can lid on the B does indeed "look" fragile. I was watching B's in the pattern at Patuxent River at 100+ knots and it does look like the whole thing should rip off, but obviously much more robust than it appears, and with so much air being sucked through the fan, the loads are not directly on the door.
I was wondering whom will be first to paint something on the inside of the lid- like the eyes on the cranked up F-8 Crusader wing. Would look great, but I'm sure the designers would cringe with the thought of paint chips going through the fan...