Well done Mark, Alan sums it up just perfectly, his rechucking is better that trying to mount in a jam chuck, the keeping the line means you are truing to what is already round, I've seen it done to a scored line to the needed diameter, then it need a little work to finish, but retain the correct size.
In short by the time you've rough turned, sized and taken the corners off on each blank, then set up a jig, which you need to make or buy first ... just to continue the turning is the way to go, well I've done them that way, it's in using the jam chuck things need to be true and it's only working so far on a face, plus popping it out the chuck.
And should the Balls need the be for the order, traditionally hand turned, would this be using a copy jig.
Mark good to read you're on the road too fast recovery.. then can't keep a good man down for long, take care in the coming cold workshop.
Cheers David