The short stocks are post-ban legal as long as the OAL of your rifle is long enough. Furthermore, the stock is only considered "collapsable" or "adjustable" or "foldable" if that can be done without tools. This is why match shooters can put those adjustable butt-plates on their rifles.. so can you. If you want more information, call Fulton Armory and ask about their "Guardian Buttstock" which is short, and adjustable.
-z