Steve Leung owner of VAS
worked with VPI and knows their stuff well. He might be able to give you some answers and suggestions.
He has a big VPI deck and like you several arm wands, unipivots, that have the mini-din connector and VPI junction box.
A compromise length is 11-1/8" effective, either JVC Victor UA-7082 or Micro Seiki MA-505L. I have installed both, prefer the JVC, but highly recommend either.

