Does the TKi4 only come with a narrow high B block or can they get the old low position with the new parts too?
That may be why he prefers the old parts.
The hole width of the B-block has not changed, and can be adjusted as narrow or wide using pills, thus it has the same width as the tki3. The only difference is that the hole is placed at a higher position giving it less kick up and higher roll center. I am sure Hara is using the wide pill position with the tki3 arms to get the original width back. The tki4, having longer arms use the narrow pill position. You need the tki3 b-block to get the original low hinge pin height.
I guess the question that I have is, a narrow hinge pin will make the car roll more, but at the same time it raises the roll center which resists roll. Will it cancel each other out, or one adjustment be prominent than the other?