I've tightened it slightly a couple times. I've never really been too sure of how much tension was supposed to be on the saddle. It was comfy otherwise and I wasn't touching the rails, so I left it alone.

Maybe on riding too far forward? I've jacked around with my saddle adjustments so many times I lost count. I have a weird build. Six feet tall but with a 30 inch inseam, so I ride a 54cm frame. On my Disc Trucker I actually have a zero setback Thompson seatpost because any setback was too much. I think I'm ok now, though. It's really comfortable except for the flaring/rubbing.