The only tiller adjustments I make are to make the bow ride steady and stable in my hand during the draw. I want to be able to place the pin on the target before I draw and have it hold steady as I slowly and deliberately draw the bow, straight back. If the pin pulls up, I take weight off the top limb. If it pulls down, I take weight off the bottom limb. I keep adjusting until that pin will hold
right there from brace height to anchor.
Of course, if you're overbowed you won't be able to perform that technique. In that case, you'll have to have someone standing beside you and watching the bow as you draw, to see whether it rocks forward or backward in your hand as you draw.
My theory is, whatever the bow does during the draw, it's going to do the same thing during the shot. Any forward/backward rocking it does during the draw is going to wreak havoc on vertical group sizes (and probably cause high/low tears during paper tuning).
That's as far as I go with tuning my tiller. Tiller tuning for group size? I don't bother with it. If I was a world class shooter and could shoot better than my bow, then maybe I would. Fortunately, I'm a mere mortal and don't have to worry about such things.
Tiller/tuning ???
