I don't know the exact size of the 12, but my 9 came in two boxes about 4'x6'x6". Once it's together, that's a completely different story. The HS on the 9 is about 10' in length and about 2' wide. Kinda hard to believe it fit in such a small box.
What many people do for storage is hang them from the ceiling when completed. It makes for darn nice wall art. What I did for general storage is create platforms over my garage doors when they are up. I have the luxury of an 11' ceiling in my garage, so after the thickness of the platforms (2x4 + plywood) I end up with about 2'-4" of space. Most of the things I need to store are actually pretty thin, so it works out just fine. I have 2 shelves of 8'x8'. Plenty of space so far.
Wings and fuselage ... well that's a different story.