I think redial deviation happens early, before THT or TTB.Sorry, I feel no maintaining radial/ulnar deviation when applying tht.. My son used ttb when he was in high school 10 years ago (when it was called tip/rip).. When he did it though the focus was on the rear scap synced with the movement as well as moving forward gaining ground.. It worked for him he hit real well 420 ... The biggest struggle was he would lose the sync on occasion due to timing and the arms/hands would take over to adjust.. I am not saying it doesn't work I see it in some mlb players, although I don't see the forced supination in any of those swings.. I don't see or feel a forced ttb at all with Bonds, Williams or any of the other great hitters.
Radial deviation accounts for 25 degrees of movement at most. Add ulnar deviation and the total deviation movement is 75 degrees. In the rear arm only, where does radial deviation take place in the swing before TTB? Do you have a picture of a batter showing the radial deviation of the rear arm?I think redial deviation happens early, before THT or TTB.
Then, assist the rotation of the barrel by applying force at the handle right from the start. Notice how much quicker the bat gets to contact. Quickness is critical. Quickness means you can track the ball for longer before committing."Also try this. .... hold the bat in the rear hand only with the hand at the height of the shoulders, the rear forearm vertical, and the bat parallel to the ground (at a 90 degree angle to the forearm) Relax your forearm. Now turn your body and watch how the bat free wheels. Turn faster and see what the bat does. This is the feel of true TTB."
This also helps hitters understand hand radius. Can use both hands too.