ballnut preload help

Trying to get my conversion all finished up and doing a final reassembly
after the move. Even with the ball nut preload set for the max recommended
(.5 turns) I still have a bit of backlash. It isn't much but it is there,
enough to feel by hand turning the bare timing belt pully. I though that it
was in my bearing block and kept taking a half thou at a time off the
retainer but was getting no change in the back lash. I then unbolted the
bearing block from the table and moved the table off to the side so I could
see the ball nut. With the bearing block just hanging on the screw I can
still feel the backlash so it has to be in the nut.

Any suggestions or comments?

Thanks,

Thomas