Saw those gas caps on a couple of camels, I guess one of them was yours. But I can't find a way to do them. I don't have that punching thing, must think of something else. Maybe thin copper wire rolled around something like 0.4 mm drill bit, and glued somehow. But gluing it on the back of the aircraft is very dangerous, might screw up everything.
I have used stretched sprue before, so I'll follow that route again. It might be brittle, but that tightenability(what?!) property takes it on top. There are a few spots, though, that require the use of a more flexible material, something that is thin as well, but can also turn tight corners. And yes, that would be my wife's hair :)
As for doubled up wires, I did them on revell's tripe, and agree that it was no fun. Sadly, doubled up wires exist on the back of the wings as well. Check this walkaround in Krakow, photo 20/23:
http://www.przemkko.strefa.pl/m_walkaround/camel.html