I originally got two FB sets, with the intention of making an expanded version, with two bays or maybe third floor, but I never got around to building it. Three floors doesn't make much sense, and a two bay design has certain difficulties. I'm in the process of bricklinking the obvious parts needed for third bay (red, white, clear doors, white door track, black back doors, floor plates, etc) These all seem to be pretty easy to find.