I bought some Tru-Turn Prop Hubs. Is it neccessary to balance them?

No.

I just got a nice tru turn spinner and back plate. They claim that their products come balanced to within a very acceptable margin of error, and I trust them. Nice stuff.

That was a great question, I used a prop nut on my Thunderbolt, and hadn't even contemplated any balance issues. I am still waiting for weather to cooperate so I can run up the Saito 100 for breakin before I maiden it.