The Spindle to pivot distance is specific to the arm being used. What you complain of is typical of VPI's tolerances. You would be best served by replacing that arm with something like an Origin Live arm. The platter and bearing are fine (VPI does not make them.) Isolation of the plinth is not good but you can deal with that by putting a sprung platform under it.
VPIs best product is their DD table with a gimbal bearing Fat Boy.
VPIs best product is their DD table with a gimbal bearing Fat Boy.