Hmm, are you saying the wings droop unless you put a load on them, and with the weight of the airplane on them they level out?
That would give me some concern about the strength of the airframe, especially once you put electronics in it. If it's just a chuck glider you may be fine, but once electronics double your weight there may be a problem. You could try adding a foamboad spar through both wings, that should give you a good amount of rigidity. If you look at the build video for the FT Simple Cub it may give you some inspiration.
I have to agree. What sort of distance are you getting on these when you fly them as a chuck glider? If they splat within about 10-15' of your launch, they're going to need some serious redesign, especially if they don't have electronics in them yet. Putting a battery pack and, per your request, 6 motors, each of which are approx. 30g a piece if you run something like an RS2202, plus an ESC for each motor, which is 4 grams per ESC, the wings aren't going to hold that weight.
Even if you stiffen the wing, now you're adding weight, which increases drag, and it simply won't fly. You'll need a larger wing area for lift and for more stability; what you're showing us currently just isn't feasible with electronics if the wings are already drooping in one direction without the added weight of the electronics. Remember, from the 4 forces affecting flight, weight affects lift, and drag affects thrust. You could have 1000 kg of thrust on that plane through tons of engines, but if the weight exceeds the lift ability, your plane is just going to drop like a rock every time you try to launch it.