My larger traps have deeps in the top and about 5-6" of space below. With using foundationless, they have plenty of time to build out the frames before I need to worry about them building below. You could probably get by with just the top frames, though your time to collect would be shorter than mine with the deeps. Worse case, they build comb from the bottom of the frames and you can band it into empty frames.
I did make a few double decker swarm traps, but these are an experiment that I'm trying. They are about 600 miles from me and won't be checked until next spring. They are 5 mediums on the bottom and 5 deeps on top. I used 1" strips of plywood for the frame rests and glued/stapled them in place. by turn the frames slightly, I could get them past the upper frame rails, straighten them out and put them on the lower rests. This won't work for you unless you put a larger space between the 2 sets. The deep depth on my upper set allowed for turning the mediums before dropping them in place.
rob...