Back on the original wire saw. When I used mine on a dead limb (about 2" diameter) I put my foot on the limb, and tried to cut by pulling the saw up and down. The end of the saw in my hands were near each other. This meant the saw was wrapped around the other side of the branch, and was contacting it over, say, a length of about 4". As the saw bit in, it got to be more than I could pull handily. Had I been a really strong guy, I think it would have overheated the saw. Brute strength not being one of my characteristics (I run more to being smart and devastatingly handsome - as well as possessing extreme humbleness) I spread my arms a bit to lessen the saw's contact area around the wood. Much easier.
They show rigging it on the ends of a strong branch, cut to a length so the branch bows outward somewhat like a real buck saw. This would then have the saw contacting wood in a much smaller area, and allow to ride rather than being pulled down into the wood as it was the first time I cut with hands next to each other and blade wrapped around the branch. That would also prevent the overheating of both the blade AND the sawyer.
Ideally, you have another guy pulling on the other end, like a real misery whip cross-cut saw. Keeping the saw stretched nearly straight automatically gives the right contact, straight across a piece of wood instead of around it. Also allows changing cutting angle to reduce the actual cutting face within the wood.