oh, this question was about chainsaws?
Okay, so I was thinking that this questions was regarding use of the Portawrap! Since that's what I was thinking, here's my response. I prefer to use 1/2, 1.5, or 2.5 wraps. I like to finish coming off the bottom. I keep the PW low on the tree. If you come off the top, sometimes the top pin will let the rope pop off, causing you to lose 1/2 a wrap. If you are holding it at belly level and the PW is just below that, it stays on better (you're less likely to lose a wrap) when loaded.
And keep it on the ground. Every now and then it might be worth it in the tree, but really, who wants to carry that thing around with them while climbing!
love
nick