The Xray balls are 3.175mm, Roche balls are 2.90mm.

I am sure you know, but for others, it is just the height of the center pivot ball (to the center) that determines the roll center of a three link live axle. The height of the links needs to match on the pod for bind free movement, but the height of the front of the links has no bearing on the roll center.

It will influence how the car handles, as you can introduce some rear steer.