The way I read it, you can have a built up wing if you want. They just have a special "added event" for all-sheet jobs.
'Cording to the posted rules, they don't give anything extra for more than two engines, so a B-17 would be self-abuse for nothing, unless maybe you built it with two enginesa nd to pinwheels. Or maybe you could build a 4-engine one, and hope to get at least two running, thereby complying with the 2-engine rule.