One problem I forsee is frozen control surfaces. That means the rocket will go in circles and the plane stage will not operate until lower altitudes de-ice it - assuming it has not already broken by then pushing against a non-moving surface.
I think you will have to do one of these:
1) provide heating, perhaps using wire through the hinge points
2) use "wing warping" for steering instead, though it would take more power
3) some other novel method of steering such as weight shift (as used by hang gliders) in a heated container. But I don't think it as ever been done in a model and is probably impractical.