My rigger runs straight with a 2 blade voodoo 7521 prop, I didn't do any offset or shimm angle to the rigger, the turn fin was sharpened that came from the rigger builder.
Try a Chris mod 2716 15* or 20*, best cat prop around but make sure your cat has the high CG setup as 34-35%, I will be going back there next month with my rebuild Insane mono, Is there still lots of **** ducks floating around..LOL
Wow, that's the fastest gas rigger for sure, I like that sponsons especially their ride pats just look like a knife, What prop and fuel are you running?