currently running a magnum 52 xls and jettstream muffler with an APC 10x7.
my question is.. would a 9x8 or a 8.8x9w or 8.8x8.75 make a noticable difference in performance? and if so which prop is the best for speed?

All depends on the motor and airframe. Different planes will like or not like certain props. The only thing to do, is buy a few and give them a try. I have a whole dresser drawer full of props that I have accumulated or time.

Tried to sell a lot of about 75 apc speed props for $50 and didn't even get a nibble. Ohh well, worth more to me

Bob B. said:
Jett tuned mufflers
Just for reference, on the 40-60L size mufflers.... when used on the Jett .40/.46/.50/.60L engines (and with other engines typically)
Standard is designed for between 15,000 and 18,000 rpm (minimum and max suggested ground peak rpm)

Prop it to run in the rpm range the muffler is tuned for. The airframe will determine the diameter of the prop so your question can not be answered with out knowing what airframe it is on.

Yeah, what they said

you have to match to the application.

If the engine setup is on a P-51, warbird, or UltraSport (etc) ....... stick with the 10x7

If it is on a Q-500 ------ sure, try any of the D-1 props you noted.

Diamond Dust or Shrike..... yeah, a C-2 series 9x7, 9x8 or the 8.8x8.5 or 9W would be worth trying.

k thanks. its on a f20 tigershark so the 10x7 might be right on the button. i ordered a few of all the sizes i noted.

good deal

read the bolly book