Too much is too much
Note what Boomer just said: That a 40F rated Burrow did him fine 11d F below its rating when he was well insulated from below.
That is exactly my extensive experience, too. The drape and seal matter much more for retaining warmth once you are protected from below. IMO, a 0F SB or TQ is needed only if you expect to be in -10F conditions. Yes, there is such a thing as too much. Too much fuss and bulk in the hammock to the extent that you cannot easily vent it. Maybe my experience is too much with smaller hammocks, but I doubt anyone with any bridge hammock would have an easy way to get lots of loft well out of the way to cool off in 30-40F temps. Where is it all to go?
Further, if you overheat, then you sweat, and now you have a garment which is harder to launder getting more aromatic sooner.
My advice is to err on too-much with the smaller UQ. On the same note: Do get a shorter TQ if you only need a shorter one. The extra length is not just of limited use; it is of negative utility.