One problem with the UCS shuttle is how tall it is if you put it on the display stand. And if the wings are down the thing takes up about the same footprint as a 48x48 plate or so. It might be wider than that actually. It is a bit difficult to find adequate space for it.
A pic I took in 2013 showing the relative sizes of the UCS stuff. The Imperial Shuttle is an absolute monster.
I think the UCS Falcon is the largest footprint though. Isn't it like 3x3 feet or something?
It's 2' x 2 1/2'