Two Beards,

I' m trying to answer from memory, as I' ve got three of their harnesses (every time I get a new Summit stand, they send me a new one).

Let' s see.... hmmm, sounds like you' re doing everything right. The prusic knot should be on your side of the loop, and then I usually snug the prusic knot up against the loop. That rope the loop is on is so soft, I' ve never had any trouble with it sliding down any of the trees I' ve ever been in; it' s always caught on the bark right where I tightened it.

Not sure if that helps; if not, I' ll run downstairs and get one of the harnesses out and look at it closer for you.