Hill, I'll gaurantee you an increase in performance with a Menz or Bolly prop. I was running a standard 20-10 Zinger on my OS 300 FS Twin in a Christen Eagle bipe and couldn't get much vertical performance. A buddy gave me a Menz 20-10 when I broke the Zinger one day and I couldn't believe the difference. Just that prop change gave me near unlimited vertical. I also like to run 20% four stroke fuel like Powermaster 20-20 or Wildcat 20%. Pretty zippy stuff.