There are two settings, prime_tower_position_x and prime_tower_position_y, I had assumed they would be the center point of the tower however I cant really work out how they relate to the circle that makes up the tower.
This is the base of the prime tower and the X Y position of it is the highlighted yellow area. Its a big prime tower as I have 4 filaments. The X kinda matches up with the outside of the brim of the tower but the Y doesn't really.
I'm getting to the center with trial and error at the moment but if there are any ideas how its calculated it would be appreciated or if it were the center point in a future update even better.