ORIGINAL: mclina
You should use fresh rubber bands every time you fly. Every other time max. Buy #64 rubber bands at Staples in the big bag. You can convert to a bolt-on wing, but it's a bit of work.
Close your needle valve all the way, then open it about 2 1/2 turns. That should give you a starting point you can adjust from.
Good luck
Under 40 degrees, rubber bands start to lose their stretch. Under 30 it is quite noticeable. Add an extra set.