My old apartment before I was married had wall racks. It's true that hanging against the wall and against the ceiling both take no floor space. Neither do wall mounted racks. Hanging from the leadouts does require a series of cup hooks (my rig), or a pipe, or even a garment rack.
The benefit of leadout hanging is that it places no stress on the structure. While balsa sheeted foam probably won't dent that much from where the plane rests on the rack, silkspan on open bays is more fragile, in my experience. Even with the foam or rubber pipe insulation, some denting occurs.
thanks,
Peter