Hi,
I'm not quite sure of the reason you can't plate onto the old chrome - it probably just won't work. As far as I know you have to strip the old plating and re-plate.
Ori
I think that increasing the span would probably work... and this is my reasoning: Larger span -> larger area -> more lift. Now assuming that the increase in lift is greater than the increase in load (weight due to the extra wing structure) then to achieve the needed lift at a given speed, you...
I don't have a good reference for you but, qualititavely, I would think that the effect of humidity on the aerodynamics of the vehicle would be through changes in density... and drag will be proportional to the density. Hope this helps.
Ori