Can't make drawing right now, but I'll try to describe my idea of variable step mechanism (I can't remember original author of variable step height, It was here on RCG some time ago.)
Hotwired solid foam wing core with rather deep step, maybe 50%. Area from step to TE/aileron would be covered with depron strip, hinged on TE. Servo arm (or some clever linkage) placed under the depron strip "LE" at wing root, to raise it up/down, changing step height. LE of depron cover strip should be reinforced with CF or wood, so it won't bend. It would be fixed at wing tip, to prevent flutter and to get step height taper.
Makes any sense?