To Balloon or Not to Balloon?

So my TARDIS dress is coming along smashingly! The question now is whether to make the shorter skirt lay flat (left side) or balloon (right side)? The shorter skirt will be cut much shorter, Tracey just left a lot of fabric on the off chance I might want a balloon look. I also think I am going to need to get a crinoline for the longer skirt.

P.S. The longer skirt is going to be detachable if that changes things?!