To eliminate air gaps, what about this: You cut the inside layer of the UQ to a pattern that will fit the hammock. Then you sew stretch webbing or straps or whatever that stretches, stretched out to length so that when relaxed it bunches up.
After that you sew the baffles on the outside of that and fill it to achieve loftiness.
This would make an UQ that fit your body like a pair of nylons, no?
Or is it just not worth all the extra effort?