I've read answers that said that the climb performance is usually worse with flaps extended, and the pilots would, if they could, just retract them and get into a clean config as soon as possible. However, i believe that applies mostly to transports, which have a higher gradient.
For designs like the Predator or Reaper UAV, which take-off and land essentially...flat, wouldn't flaps be more beneficial to help their climb? Albeit, having to reduce their deflection at intervals to reduce drag?
And if so, what do you think would be the altitude at which retraction would occur? I've tried to find information, but so far have only landed with a Boeing document that claims the typical flap retraction height is 3000ft.