RE: Propeller conversion chart
I generally agree with Minnflyer but this 2 to 3 conversion thing is not that simple.
You need to go back to basics. At what sort of rpm does your particular engine work best? Not easy to establish but you probably did some rpm tachometering to establish which prop gave you the best rpm's for the best power output.
the same principle applies to 3 blade propellers. You need to buy a couple andtacho them.
Remember a 3 blade is heavier and less efficient but produces more thrust. SO I'd start where Minn has advised you to but also consider a 12x6 three blade and everything inbetween.
I believe those would be 11x6, 11x7 11x8, 12x6, and 12x7 even a 12x8.
We recently (yesterday infact) tried a OS55AX with a 11x7 3 Graupner which was supposed to reduce the speed of the trainer. Wrong it went like a scalded cat and thats with a 55AX at nearly slobbering rich high speed setting. It behaved likea 11x7 two blade prop bu with more pull on the vertical.
My conclusionis that its not as simple as drop inch in diameter and increasing one inch in pitch.
I'm tempted to try a 12x7 3b on my Extra
Trail and error