Well let's see. On an .099 I used a 7 x 4 so on a more powerful OS .10 I'd try a 8 x 4 or a 7 x 5 for a start. I'm not sure it can handle a 9 x 4, but you never know. Anyhow, experiment with those I mentioned. Others will come on with their input.
I have no specific knowledge at all, but I anticipate that you will have a problem finding a prop that provides the right combination of RPM and in-flight speed. I expect the issue will be that you need 7" to get decent rpm, but 4" of pitch will be way too much. If you can find a sufficiently robust 7-3, that's where I would start.
You can also use reduced diameter to decrease the efficiency. I think you will find 8", and possibly 7", too efficient. I am sure you could start it on a 10-6, but the big mistake people tend to make on modern engines of all types is trying to run too much diameter. That went out in the 4-2 break/ST46 era. You need to rev up to to make the engine happy, and that will more than make up for lost efficiency. IT must be extremely inefficient in level flight or even a .10 will pull the airplane far too quickly if it hooks up all the power it is capable of. The alternative is to detune it to remove some of the power, which is what the Head Gasket Patrol and guys with Dremel tools attempt.
This is true even at the highest levels. Dave and I are running *much* smaller props than the engines will safely manage. I made the flyoff for the first time and finished 3rd in 2000 running what was previously David's "break-in prop", after having buzzed it down a few times. It wound up at 11.25" - on a PA61 capable of the spinning same prop at 13.5-14". Same with year I won, I buzzed the prop on Top 5 day, didn't even clean the end up, and it was down to about 11.75 - from 12.5.
Brett