Which prop for a Mac 90 engine?

[joeheli]

I have been asking couple of my friend about the best prop, diameter and pitch for a MAC 90. I already know that Rick and Mike use a Tennessy 52"x26". Here were I live we use 50"x 30", I use a ST. CROIX 50"x 30"But my max RPM is 3200.I lost one of my spark plug and the rpm drop 200rpm, the gyro at full power was goin down. That told me that I am under the power curve. Knowing that the mac higher rpm limit is 4000 to 4200 I know that I have to chage the prop size and pitch. For you guys that already experiment with your Mac, Which blade has work best for you ? and What max rpm do you get and temp? I really don't want to be under the power curb. And really don't want to BURN my engine (over heating). I really apreciate your good info.