Gary, you don't beat the snot out of wedges when the tree is cut up 50% of the back cut, your fighting the tree too much, and you don't have a 'hinge' yet you've got a huge block. It won't hinge on that much wood. When you have the hinge right, the wedges tip the tree. Wood is crazy strong, that's how trees stay up.
Same thing with a rope, you don't pull hard when your 50% through your back cut.
Before I start pulling I have a mental picture of what the hinge should look like, maybe 10% thickness.
I'll put a minor tension on the pull line,
then cut the back cut a good portion, and set (not drive) wedges.
Set wedges before it can sit back though.
As I get closer to my final hinge thickness, I'll be able to tell if the tree is sitting back, neutral, or pulling forward.
Sometimes, you might find it worth marking the end of the back cut/ beginning of the hinge with the bar tip in advance (vertical kerf), taking the full judgment of how much is the 'right amount of hinge' away from active cutting and pulling action. This serves as a good reference mark for a spotter, helping everyone not to misjudge how much hinge is present when using a stump shot. Often an uneducated spotter will tell you how far to the face cut, not the front edge of the hinge fibers, leading to a thin or cut-off far-side of the hinge.
If it's sitting back, apply a bit more tension, without lifting the tree much, and/or snug the wedges.
If it starts to open up a bit as you cut, snug the wedges.
When I'm in the right hinge thickness ball park, I'll often bang the wedges a couple times. It they drive a bit, with more of a low pitch thunk, your definitely winning. It should tip right over on the hinge with a pull.
If they don't drive in well, but rather have a lot of rebound with a higher pitch, you're going to need a harder pull. Driving wedges and pulling helps tip the tree from two efforts. This can be helpful if you are afraid of breaking a defective tree, losing traction, or over-loading your rope/ puller.
Wedges kept snugged up tight with a pull protect in case the rigging breaks or traction breaks.
If you're fighting side lean, you need more hinge. If you are pulling against the lean, directly, you don't need as much (you could get by with an overly thin hinge, it you really pushed it).
Bending wood is hard work. A thick hinge takes a lot of force to bend, independent of the weight of the back leaner. Say the weight of the log take 100 units of force to tip on a friction free, literal metal hinge. In real life, you have to add the force to bend the wood hinge. Arbitrarily, let's say a 10% hinge takes 30 units of force to bend, and a 25% thickness hinge takes 100+ units of force to bend. You are needing to generate and use rigging to support 130 vs. 200+ units of force to accomplish the same goal. A 10% hinge is pretty much not going to be crushed to failure no matter what . Side lean would have to be substantial to rip a hinge off at 10% thickness.
We had a bunch of really nasty cottonwoods to fell at Parks. 6' dbh, 4-6" solid green wood shell, hollow as a drum. As my partner cut up the pretensioned tree, chasing the back cut around, basically with the saw plunged in perpendicular, I slapped in every wedge i could to support the tree, and not build all the weight only on the little bit of hinge wood on the two corners, potentially crushing the stump under the weight of what was left in the crown after getting everything (big laterals)possible with the 60' bucket on a 130' tree, aka Sh*!-ton of weight getting concentrate on the hinge. The winch pulled it over without the stump or log buckling. My partner climbed in that stump.
