The good thing about the rotor os you can glue the shaft into the top of the housing and set the completed rotor head down onto it. I try to build the rotors so they can be removed, if I'm lucky enough to have a contest quality build to show, but like you, I'm limited on space. The heli's can sit side-by-side while their rotors hang on the wall.
This will be very handy when I finally finish my Halo, this thing is a monster.