Scope is raised to the end of adjustments and bullet is still approximately 8" low do I shim back base?or front base? Thanks for any help

Raise the rear base.

Thanks mudhen I changed bases and rings it worked out doing this

you have to think of it just like iron sights

Rear sight/base is moved in the direction of the correction.
Front sight/base is chasing the bullet. i.e. shooting low, you lower the sight.