Double washers were the ticket for me.
A single washer just made me pull my hair out.
Craig, is that a 6” vise?
5".
After 4 hours of getting some very confused measurement results @Dabbler finally figured out the cause of all my problems. Ends up there is sufficient play in the x-axis Gibb that the table moves as you're trying to square the vise. John will be able to explain it better than I. Until we come up with a plan as to how to resolve that issue I'm going to have to live with vise not being as square as it should be.
Thanks for all of your help with this John.
Craig