Coug, I'm not familiar with Gorilla's specifically, but I'd assume it hooks up the way all my Seat O' The Pants harnesses do...

I found that if I hook up so that the attaching rope is high enough on the tree so that it's just barely taut -- or about to go taut -- when I'm sitting, I can still comfortably move around while sitting down, but it gives me the most flexibility in turning from side to side in a standing position and keeps that hookup rope out of the way the best.

And I've tried EVERY way to hook up to a tree I can think of.