I would think low diamater, high pitch for higher speed aplications.

Got the cap with the DL out again today. I FINALLY got the hang of the flip start and am getting it to start within 5 flips. Just a different process that takes getting used to. The engine is running great. I was having a little heat problems so i need to open the cowl up more. I am going to try and expose more of the cylinder head. Hopefully that will let me lean it out a little more. The engine seems to be getting better each flight. I got 4 flights on it today. Really impressive verticle at the moment (to me that is all that matters) and i am hopeing it will get better. I think i have around a gallon run through it.