Robin,
If you look on the thread "Saito 30 Black Knight" Bob Z indicates that 9x6 - 10x6 work fine with the Saito 30. I have used a thin blade 10x6 on my OS 20 with good performance. Your fuel seems OK.

Best,    DennisT

The Saito 30 is a very forgiving and flexible engine.
I have around ten of them and I have flown them in quite a few different aircraft, including but not limited to Flite Streaks, a Sterling Mustang, the prototype Brodak Cardinal profile, a Nobler, and my favorite, my own design Little Cherokee.
The engines have run well on a variety of fuels: Powermaster 20/20 all synthetic, Brodak castor/synthetic (both 10 and 15% nitro) and Powermaster 10/22, 50/50.
Regarding propellers, I did a lot of experimenting with different diameters and pitches and the ones that the engines seemed happiest with were the Master Airscrew 9-6 plastic and the old Top Flite 10-6 wood. I even ran an old Top Flite 9-8 wood on the Sterling Mustang but the little .30 wasn’t too happy!
In any case, try and find what combination of airframe/prop/fuel works best for you.
For what it’s worth, I would not go below a 6 pitch.

I hope this helps.

AND, for what it’s worth, no matter what anyone tells you, ONE TEST IS WORTH A THOUSAND EXPERT OPINIONS.

Bob Z.