Not going for ultimate performance really.... its a scale plane my radial will be installed into. There is an old video of a soloprop 20" and asp FS400 combo on a CMP Zero on youtube flying very well with excellent sound too. will use the solo IF I need the extra nose weight and flywheel effect, the Xoar if I need less weight as it is a very light but rigid and efficient prop. I have used 3 blades before and you are correct, they are not as efficient on higher revving engines as a two blade but check out my top flight 60 P40....plenty of performance on a 16X8 3 blade Master Airscrew, later flew with a 16X10 3 blade and will campaign it this year with a 17X8 Xoar 3 blade. the 16X8 was beat to death by the YS 120AC and 30% nitro as the prop was supersonic all the time at full throttle. The 16 X10 3 blade gave better performance but I believe the light 17X8 Xoar will do very well this year. Pic below is my P40 with the 3 blade flying prop from last years season.
ASP +solo 3 blade 20"
http://www.youtube.com/watch?v=zrN5o188rAs
Pix below is my P40 with the 3 blade flying prop from last years season. Check my vids on my youtube channel for incremental mods done to the p 40 over the last few years including my maiden, yup, on a 2 blade APC 15X10. With the 2 blade it was unlimited vertical, pretty impressive in a 14 lb. 60 sized airframe. 3 blade are not quite unlimited on this ship but close.
My P40 with H9 P40 playing with the moon. 16X10 3 blade Master Airscrew. Most of the flight is half throttle to 2/3rds.
http://www.youtube.com/watch?v=n7IxM...Th6XA&index=16
One full power pass here, supersonic with 16X8 3 blade Master airscrew, timecode 03:18 during the 2011 season. 2012 I went to a MAS 16X10 3 blade.
http://www.youtube.com/watch?v=2Uk0J...LTh6XA&index=7