“I keep going back to my Gossamer Gear Mariposa, though, because it is so light. The backside on it is pretty flat. I've had pools of water from sweat accumulate on my sleeping pad,”

I love this pack. However, I have the sweatiest back so I used my Ghost the most (very good ventilation).
Then, I ‘fixed’ the Mariposa and now my shirt stays dry <img src="/forums/images/graemlins/shocked.gif" alt="" />. And thus I find myself taking the Mariposa more often.

I use the sit pad as the frame with the bumps into my back. I take out the stays (it fits more comfortable that way). Tucked around the sit pad is a 2.0oz car-drying towel. I am surprised how well that towel keeps the sweat pulled off my shirt. At a rest stop, I feel my shirt and it is dry. The towel is soaked and I wring it out. I use this towel also for showering, and drying my tent.

I also have a golite pinnacle. This doesn’t have a back frame pocket to hold a pad (and thus my towel). So to cure my sweat problem with this pack, I put my pack on and then I ask someone to tuck my towel in between my back and pack. It stays put the whole time (until the next rest stop).

-Barry