The facecut is like a pressure relief, allowing tremendous leveraged force to flow in that direction. It's shape reminsicient of a tire chock built to hold force back. Without facecutting is allowing that force to build up back pressure and split, barber chairing etc. Just as directly in line to the rear is the most leveraged pulling restriction, the farthest outward point of tree circumfrence in line with the fall, is the most leveraged pushing restriction (face). Both are most leveraged positions of passive force restriction, showing the power of each these twins here, in the example of the face cut on the one side.
On suspect toppings (split, dead, weak species etc.)sometimes i put a sling around 2 x, and get it basketed around tightly on a karab in long axis position, then leverage the length of the karab to stand out perpendicular to spar, so sling (perhaps series of loop runners) tightens even more. sometimes i lock it around a stob to stay in position, or even hook to belt for support too. Lean back to maintain sling set in tightened position on spar. shouldn't split that stuff on the scale i play at, and if it did, i think id, be alright,a s it let go of karab.
When rigging out on cracked spar, block/top and catch, have found that the choking action of the pulley's attatchment to the spar helps keep the cylindrical solid shape, aiding in preventing cracking.
Trucker's 2" webbing and ratchet is about 10k, is pretty good too. Especially when final tightening is with empty drum; point of most mechanical advantage/ leverage. Same as using come-a-long to tighten, maintain cylindrical shape, empty spool is most leverage; but come along needs a couple wraps so main pull goes to friction on drum and not mechanical stop on end of cable in to drum(weakest point), with the most pulling leverage the device could muster(empty spool).
One emergency job i did that at night with 2 binders, then put a line on worrisome limb over house, close to it's center of balance; gave direct overhead support ran line across top of the tree over column of direct support through trunk, tied to limb on the other side with tight line. Then cut that 2nd limb off to hang on the safe side, to support the limb over the house, even dampen motion nicely. So i could do it more safely in the light, for it was huge, wet, with more rain in the hour. Also, so i could disarm the one next door quickly!