Hmmm...
I'll just give my opinion, not worth very much as I'm not really a pro and I'm sure there's a lot more good advice from people that know a lot more than I. I guess the fist thing to realize is that it is a different game than taking a tree down from the ground. Your' suspended from the tree with no way to run if something does go wrong.
First and foremost is safety and there are a lot of little aspects to that. I'll try to give my two cents on that after saying that you really need to be comfortable and have an expected outcome of your actions but also be aware that things don't always go as expected and be prepared for the "worst case" scenario. Realize what could go wrong (I'm not saying dwell on it, but realize and make note of things that could happen).
an safety, of course the PPE, this in my mind extends a little farther than the usual stuff you have on on the ground. Good climbing equipment, ropes to get you out of the tree should something go wrong, People on the ground capable of lowering you to the ground if god forbid something did happen and you were unable to do that yourself. Two tie in points anytime you're running that saw in a tree are good advice I think. also certainty in which direction you want that top to go. Winds play havoc on sails up in the air so I believe it's best to take a little extra time and install a pull rope above where your going to be cutting that thing off. as far as the face cut and where to stand. My personal preference is the usual 1/3 of the tree. either humbolt or conventional whichever your comfortable with will work fine. With a humbolt. Which one makes the top sway more when it snaps I'd say is debatable and likely won't ever be resolved. As to standing slightly to the side or directly behind again I say whichever your comfortable with or the situation demands. After that face cut, you should have a pretty good idea of where that top's going to go sailing down at this time I usually make sure again that there's no ropes/ obstacles on the ground/that everyone knows that the next time that saw sings somethings gonna happen and I shouldn't have to say this, but I've seen the ones where the guy cuts off the limb he's standing on so make sure again that there's nothing tied to that top that shouldn't be, that you're comfortable with your tie in points etc... (as a side note don't know if you're running a top handle or regular saw, but I see a lot of guys with just one hand on those top handles and even though they lend themselves to one handed operation I don't think you should ever have just one hand on that thing. on the back cut leave that strip of holding wood nice and even side to side and cut till your sure it's committed to tipping over shut the saw down before she does get comfortable and relaxed and ready for a little shake and enjoy the sights the sounds and the view from the new spar.
Just my two cents,
