well I've never seen an opti-pac myself.
I would imagine that it interfaces pretty much the same as mine does to my ME-4 from hagstrom electronics (via an 8 pin connector on the opti-pac?)
hagstrom sells a trackball adapter that replaces the existing wire harness that comes on the happs balls:
http://www.hagstromelectronics.com/accessories.htmlKE-TBH3 (cable I'm refering to)
simply disconnect the 4 pin plugs on the optic boards for the trackball and connect the KE-TBH3 4 pin connectors in their place yellow/green to "y", and purple/blue to "x". the cable is 3' long and ends at an 8 pin connector. the pin size is the same size as what is on oscar's pro spinner. Not sure if this helps or not, but hope it does.
ME-4 (not cheap...about 50 bones)
the 8 pin at the top of this pic is where the trackball connects, the 5 pin next to it is for a spinner