If you really want to make sure that your not overpropping it---but you want to get some thrust out of it-----use the Menz Ultra 22-8.

The Ultra is a narrow blade when compared to the S props from Menz.

I run a 22-10 Ultra on a 60cc engine. They put out PLENTY of thrust. Don't be afraid of the Ultra. And don't let some idiot at the local field tell you it won't pull or have any thrust because it's not an S blade or a Mejzlik or an APC or whatever.

Buy a Menz Ultra 22-8 and try it out. You will allow the engine to spin up and you'll get plenty of thrust for good flying. It's gonna spool up fast.

Thats what I'd really, honestly do with that engine. A Menz Ultra 22-8. If you can't get it up in the 7000RPM range--then drop to a 20-10. The smaller disk (diameter) will allow you to get the RPM up where you need them. I'll bet the 22-8 will do it--but if not, then drop to a 20-10 for a couple gallons. As the engine breaks in, it will get stronger and gain RPM. When it finally gets up to 7500RPM--then slap the next size bigger prop on it and slow it down to 7000RPM again.

It might work out like this:
20-10 for break in. Maybe 7000--7200RPM. Just guessing, but I'll bet I'm close.
Let it run like that for a few gallons. When it gets up to 7500RPM on the ground--switch to the Menz Ultra 22-8.

I'd just buy any ole' cheap 20-10 for break in. Buy one with a standard blade or a narrow blade. Don't slap a boat paddle on it with a blade that's 2" wide. Get a cheap Zinger 20-10 and run it for awhile. You won't have gobs of thrust--but it'll fly your plane just fine.

When the RPMs get up to 7500--then switch to the 22-8 Ultra and slow it back down a bit.