Has anyone played around with using a warmer UQ for the given temperatures and a lighter TQ?

I am thinking that since the insulation under you is more important for warmth than what is on top of you, that for nights that get down to 40 degrees or so, if a 20 degree UQ might mean that I could use a very light TQ or blanket, etc?

Granted, warmth is a personal thing, but just checking to see what people think of this idea. It would save me from having to buy different weights of TQs.