It's been a couple of years since I've used my Speer Hammock + Snugfit underquilt.
I had forgotten just how well that UQ fits the bottom of that hammock. There's just no potential for air gaps because of the way it's attached along both sides of the hammock with Velcro.
One of the gear makers that make underquilts should run with that design and try and make it weigh less or maybe even make a 3/4 length one.
I'd buy it, that's for sure.
(It's kind of pathetic that I wake up in the morning thinking about this kind of thing...)