UPPER temp limits of sleeping bag comfort?

I'm really only comfortable about 10-15 degrees above my quilt or bag's rating, and 15 degrees is really pushing it for me. My first bag was a 15 degree Marmot Sawtooth, and even in the mid-30s, I'd wake up sweating. You're right, it's hard to find an equilibrium at a certain point. Draping and venting can only do so much, for me at least. Excesivelly perspiring in a down bag isn't a good thing, either.

I changed to a 32 degree quilt, figuring it would be easier to push it lower with extra clothing than it would be to make a 20 degree quilt comfortable at 45F. I spent one night with that quilt when it was in the 60s, and lucky for me I had brought a bivy, as I ended up sleeping on top of the quilt, with the bivy and my clothes enough to keep me warm.

Now I still have the 32 degree quilt, a 40F 2/3 quilt, and a 5 degree bag. I think ideally I'd squeeze a 15 or 20 degree quilt back in there if I could afford it.

I used a 35 degree bag in 55 degree weather and it was annoying, pretty much as you described.

Looking at EN charts seems to also suggest about 15 degrees above rating before going into darker red.

Bag is only part of sleep system:

example:

tent closed up, long underwear, puffy jacket, thicker socks = 15-20F
tent closed up, long underwear, bag cinched up tight =20-25 F
tent well ventillated , long underwear, bag cinched tight, = 30F
tent well ventillated, long underwear, bag not cinched up = 40F
tent well ventillated, long underwear, bag open at foot and neck = 50F
tent well ventillated, no long underwear, bag open at foot and neck = 55F
tent well ventillated, no long underwear, bag unzipped = 60F
tent well ventillated, no long underwear, bag used as quilt as needed=65F-70F

Now can add variable of shifting down from top to bottom as well and customize it even more if have bag with continuous baffles.

I am in San Antonio, Texas, and it stays quite warm throughout the night here and in much of the surrounds. I really appreciate the post above, looking at various configurations depending on temp. Not hiking right now (recovering from ankle injury), but as I'm a "hot" sleeper, when I head out I was planning to leave the bag at home and use a tent plus either silk or CoolMax sleepsack (I own both). I would love to hear additional tips or arrangements for comfort in hot weather sleeping (especially a barrier over the sleepsack that wouldn't leave me sweaty and uncomfortable)…

ive never had any issues …. if its that warm, just sleep in yr insulating clothing or cover the core of yr body

a 20F quilt would have the same issue as a 20F bag unzipped and draped

For warmer weather desert trips I usually take a narrowish silk 2.5 oz Apex quilt and no other insulation. Very breathable, nice against the skin (not clammy like nylon gets) and light.