Burnham
Woods walker
I doubt that's what Darin means.
Pulling the slack out as the piece tips over lowers the load by shortening the drop...that's one great feature of a ratcheting bollard. That's different than winching it tight before cutting. Does the GRCS work that way?
Tying closer to the midpoint of the log above will maximize that gain. On a 10' log, you could pull in almost 5' of slack.
The idea behind pulling the slack it as a piece goes over is start catching the load earlier, lengthening the distance over which you are slowly catching the load, making it a smoother catch. Think about a piece that is tied ten feet above the block. If you let it free fall, it drops 20 feet before loading the line, achieving greater speed and force before you start capturing it. If while it is falling the first ten feet you take what slack you can up, you shorten it's free fall and start the capture earlier. Taking up the slack reduces the amount of force you have to absorb by slowing the fall.
The idea behind pulling the slack it as a piece goes over is start catching the load earlier, lengthening the distance over which you are slowly catching the load, making it a smoother catch. Think about a piece that is tied ten feet above the block. If you let it free fall, it drops 20 feet before loading the line, achieving greater speed and force before you start capturing it. If while it is falling the first ten feet you take what slack you can up, you shorten it's free fall and start the capture earlier. Taking up the slack reduces the amount of force you have to absorb by slowing the fall.