NEMO - Jazz Double Synthetic Sleeping Bag

You say your clothes are optimized… but Nemo jazz is a 30deg bag and I’d be shocked if you tried a zero deg quilt with the right layers and couldn’t make it work. I find my 0deg quilt plus alpha fleece and wearing my (dry) rain gear is good well below freezing even cowboy camping with a breeze. But you gotta practice and iterate. TLDR: the bags/quilts you tried might not be your problem.

Since it’s temp controlled, I think any sleeping bag will work. I think it just depends on your budget. I have a Nemo jazz that I use for regular camping. When we sleep in the car- we just use a sheet and a blanket. Good luck op.

I believe the NEMO jazz does. Amazing quality, will last a long time, and made to be a wonderful luxurious bag

My 30° Nemo Jazz on a cot with a Thermarest Luxury Map XL keeps me super warm in those temps with just a merino base layer.

This. I hate mummy bags. I move too much in my sleep. My Nemo takes up a bit more space in my pack but it is so comfortable and a good night’s sleep, where I can fully roll around in my bag, is worth it. I will never go back to a mummy bag.

It might depend on how you're built, but I can get my leg up like that inside my Nemo bag. I have short legs, though.

I really wanted to love the Nemo, but if OP is a smaller person, Id warn they have too much dead space.

I'm a side/stomach sleeper and love my Nemo sleeping bag. I have a synthetic one and it's quite bulky, but the down ones would compress better.

This! I love the little zippers on top to help with warmer nights. A knee is always moving up or down and I have just enough room for that at 5'10.

If your biggest concern about a sleeping bag is room for your legs to move without feeling constricted, I would try out Nemo or Big Agnes sleeping bags. Both tend to have wider profiles. Definitely go for a bag that is rated at least 10 degrees lower - preferably lower - than the temps you expect to sleep in. Theres multiple problems with layering with clothing like this, one of which is not the warmth specific factor but the breathability. One or two layers is one thing, but with all the listed clothing and then something like the picture on top, you’re going to build up humidity near your body you can’t get rid of, and you’ll become even colder. Next, a sleeping bag basically creates a warm pocket of air around you. The insulation in the bag helps create and maintain this pocket. The more compressed this insulation, the worse it performs. With layering clothing, you compress the insulation, making it less effective. On top of that, insulation is minimal if not nonexistent at the seams. Some puffy jackets and “extreme temp” clothing gets around this by minimizing seams but there’s almost always a few somewhere, which means no air pockets and no warmth. If I could recommend the best case scenario for you, it would be this: find a sleeping bag you can tolerate rated to a temp appropriate for your conditions, 15F at a minimum, best scenario a 0F. Dress in only your smartwool layers, and make sure you have a good pad/sleep set up underneath you. Sources: avid outdoorsmen, backpacker in sub 20 degree temps, and former REI employee who specialized in camping gear.