It's hard to believe so much can be said about rubber bands, but I'd like to add: if you cross the first one, the wing will hold flat without wanting to tip off. So I usally cros the first set, then put a couple of sets straight, then cross the last set to help hold them on. If you put too many or too strong, you're defeating the purpose of the rubber band method, which, in the event of a crash, is to allow the wing to come off before it breaks.

Phil