Both Super Sicroly and Curare use the combined flap/spoiler, both MAN and RCM&E plans illustrate the concept. I fly both models, Hanno says there was no trim change when actuating the flaps, both of mine go nose up, controlled by simply closing the throttle a bit more. Landings without are quick, landing with allows you to drag the model in pretty slowly so if it's windy you don't ned them, if it's a bit calm it certainly helps. I haven't used them in flight (spins) as I can't think that fast (which switch was it?) but they work really nicely in the circuit. Construction is balsa and ply, no cf or glass needed as they aren't very big, and there is little aerodynamic load on them. Standard JR 517 servo is more than enough power to get them down, even at full speed, but watch the nose-up trim!
Evan, WB #12.