Temp limit on sewn- thru bags

It really depends on how hairy you and most importantly your nads are. Just think, cave men didn't have a bag, but they sure were hairy. Either that or bring your fat girlfriend to keep you warm. Oh yeah, and a good pad trumps all.

So do you use a sewn through bag Alex?

I'm noticing they are typically limited to temps above freezing.
Like for example, the WM Highlite sewn-thru bag is rated to 35*F(previously was 40*F), and the WM Summerlite continuous-baffled bag is rated to 32*F. There's two ounces more down in the Summerlite too, but it seems that there was some reason for them to change to continuous baffles in the Summerlite to get those 3 degrees lower.

So, I'm gonna say "above freezing".

I have a WM Mitylite with overfill that does me fine to freezing, but I'm hairy.

"I have a WM Mitylite with overfill that does me fine to freezing, but I'm hairy."

I am hairy too……but I would freeze ;)

Seems like a shame to carry the extra down around without getting the benefit from it.
Why don't you see if you can get a cottage manufacturer to use the down from that back to make a nice 3 season baffled quilt?

I bought a like new hilite and could totally feel the sewn through seams in it at over 50 degrees. It was not warm at that temp, not cold, but not warm either.

I sold it after one night sleeping it and got a summerlite, with real baffles, almost the same weight and a far better bag in my opinion, plus not being able to use the hilite like a quilt in summer because of the partial length zip made it even more pointless.

Glad some people like those bags, was easy to sell, but I wouldn't ever use sewn through again, just lose too much heat that way.

Keep in mind, the question is really, how warm is a pertex layer at night? The answer is, not very. Since the seams are basically just a pertex layer, nothing more. Weird idea for a sleeping bag.

I wouldn't call her that.

This is just an anecdote, not any real data, so it may or may not be useful to you. :)
I grew up in a house that was kept at 50 degrees or less inside in the winter and I remember being very unhappy with down or primaloft comforters which had sewn-through boxes. I found it very unpleasant to have patches of warmth interspersed with cold spots – more irritating and difficult to get comfortable and fall asleep in than in a not as lofty comforter that did have baffles. Now, this was inside, in a bed with a solid headboard and footboard. If you're outside, there's going to be a bit more moving air. In my experience, if it's cold enough that I want to actually sleep under/inside the comforter/sleeping bag/quilt instead of just draping it across a bit of my body, then the sewn-through places are noticeable. I doubt that this is a safety issue at warmer temperatures since the body is good at evening out the temperature of parts of it that are close together, but it sure is uncomfortable.

My thermodynamics intuition is that it would matter less with a hammock underquilt, since your body isn't right up against the cold spots. I think (I'm not a hammock user, so I'm going based on pictures here) that there's also a bit of an air gap between the quilt and the hammock fabric everywhere except around the periphery where the quilt is fastened to the hammock, which would serve to insulate you from the thin (thermally conductive) spots in the underquilt, since still air is insulative.