One of mine came on an RTF (Naboo Fighter) with a 6x3 installed. I prefer to load it a little so I don't have to reset the ball socket so much. I prefer a 6x3 for two-bypass reedies, and a 5.5x4 to 6x3 for single bypass. Of course for performance you may want to let it rev.

I also run 15% nitro mostly. Many like more nitro and less prop. Your choice. Keep the lube up to ~20%, at least half castor.

Bear in mind that these are one person's preferences.

George