DavidT,
Let me be clear about my response, because I don't want you taking it the wrong way; I completely meant what I posted but it isn't directed at you in any negative way. I'm sure you have a fine sense for the techniques and hazards associated with falling a large tree. It sounds like you have assessed the situation clearly and developed a plan for safely removing the tree. If I can add one piece of advice to the posts already given, I recommend having a second (and even a third) chainsaw on site for completing the back cut. Often times in residential tree work, the large diameter wood has some chunk of steel or garbage or God knows what stuck in it somewhere. There is no joy in watching a massive tree almost felled just hanging there like a piece of bad news.
As for the definitive tone of my earlier post, I meant that as a kind of wedge against the word salad explosion of ideas and information - good, bad, or otherwise, that you typically receive when you ask a question like that. If you really weren't sure about how to get that tree over, you would quickly have enough technical expertise directed your way to put you in a wheelchair for life. And most of the information is right on; but in the wrong hands it can wipe you out just the same.