If you'd be so kind, please chime in with your anecdote about whether or not you use a groundsheet under your neoair in shelters on the AT. When I hiked from Springer to Greenwood Lake, NY, I used an X-therm with no problems, but have since up(down?)graded to the X-lite. I remember seeing about half and half - with/without groundsheet. Haven't been hearing of many leaks recently... do you think the thinner fabric even makes a big difference? Is it more about the seams, etc.?

thank you, kind people