Another perspective
First off, Serial I am glad you have that ability to "fast forward" and predict what is about to happen before you put things in motion. That is why you need to remove this 16" limb, you have determined it will be trouble. Have you "fast forwarded" the cutting of just the limb? IF, that limb grows out horizontal (parallel to the ground) for a bit, and then curves gently upward for a looooong way which would be very typical of walnut, the tendency will be for the butt to jump back up into the tree quickly as the weight of the tip pulls down like a teeter totter. This happens quicker than you can swing out of the way. It is even faster yet if you are not expecting, (but seems like slow motion).
Since it seems you are determined to go ahead with this alone, and taking in sections implies even more advanced aerial work, you might just treat it as you would a heavy headleaner that you are trying to fell off at a 45. With a very wide notch, and thick hinge wood you can make that limb just sweep sideways to the ground and not even break the hingewood. Then just walk out and whittle from the tip back. Should have a large enough diameter to plunge that back cut and finish with the tensioned strap, so the thing does not barber and split into the log anyway.
GOOD LUCK and GODSPEED