My 3 layer IX works for me down to the low 30's (max), so you could get to 25 ok. I also used a 1.1 rip stop on the bottom only. People tolerate cold differently, so ymmv.
In order to really be effective, I had to make a top cover to help trap body heat inside the hammock - that was worth 5-10 degrees by itself and worked wonderfully. Just remember that IX is a vapor barrier and can lead to condensation problems. I had just a little condensation in mine but it dried very quickly.
The forth layer at 42" should work ok.
I got in a fight one time with a really big guy, and he said, "I'm going to mop the floor with your face." I said, "You'll be sorry." He said, "Oh, yeah? Why?" I said, "Well, you won't be able to get into the corners very well."
Last edited by Lost_Biker; 03-04-2012 at 08:07..
Reason: Added stuff