Hi OVA,
Maximum is 1.75mm with AT21ST-A balls that are 0.5mm lower...so 1.25 with regular AT21...so no crazy high roll center here.
Caps are regular P03 with OR14V o-rings.
I really need to put this car on a track and see what I need for roll center...I am already working on a revision of the part I want to push the swaybar about 3mm more in the middle of the car. This will probably help to have more clearance on top of the P03.