I'll put in my 2c's and agree completely with Scott. In my many, many years as a timber faller in Oregon and Idaho, I of course, got to see similar scenarios on occasion. Even now, working as an arborist, I run into the same thing at times.
A real problem is that when the top is suspended as yours was, there may be quite a twist and "back pressure" or compression, on the log. Cutting from one side then the other-top then bottom in this case-can still get your saw pinched as the top rotates and pushes back toward the butt! What we recommend is that you cut down from the top, say 1/3 of the way thru, make another cut from the top so as to remove a narrow sliver maybe half or 1 inch wide, then cut the off side very slightly, an inch or two-be careful and brave on that one as you are reaching under the log-then finish the cut from the bottom. I like to make that top cut to the point where I just start to sense the chain beginning to bind slightly. It's really easy to go too far with that cut, so quit sooner rather than later. Ha!
I just used this technique Saturday for a local landowner on a cottonwood of his that was hung at a 45 degree angle into another cottonwood, and still attached to the root ball.
When stuff starts to move, it moves very fast, so have your escape route(s) planned and rehearsed. Have fun! Be safe!
