I use the Freetom Harness (well now its the Funnel Harness) from Packer Locker.
It is all elastic so theres no orings to damage the shaft . Ive used it with Freetom, peecock, emisil, and ec prosthetics. It holds everything where it needs to be and also supports any flappy tabs. It was like $20, but their running all sorts of specials right now with the new owners and everything.
Most of the harnesses and packing underwear tranzwear sells has thick C Rings which are not very flexible. These can cause very serious damage to your prosthetic (no matter if its cyberskin or silicone, but honestly its better for cyberskin). Even the rings PL uses are softer and more flexible to cause as little damage as possible