HellsCanyon
WKR
I just had a thought that the same noises coming from my T1 MIGHT be happening when I've totally saturated the back of the back with sweat and had a pretty heavy load on the pack. Enough to be using the load lifter straps substantially... I'll pull the stays this week before heading on an elk hunt this weekend and will let you know if I find any difference. Like you said its been too random to totally nail down the cause of it.
Mike
Mike