What props should I try?
 

My 496MagHO powered Dominator has labbed 30's on it, but the best rpm I can get is in the 44-4500 range(unless I get too aggressive with the trim). It'll run about 76-77 on the GPS with them. I was wondering whether I should drop back to a 29 or a 28 in order to get a few more r's and hopefully a little more top end. Any suggestions?

Go back to your 28P four blades the way it came. The labs even if they worked to give you that 1 mph, will in the long run cause headaches from being expensive, and more importantly, fragile.

Also remember you've lost a some rpm just from the heat and humidity we're exeriencing now. Best time to dial in props is early spring, or late fall when the air cools and gets more dense.

What's a good source for buying props? The pricing I'm getting from the local shops are pretty steep. Should I stick with Merc's?