I have tested some props on my OS-200S. The engine was not fully broken in at the time, but it will give a hint
3-blade (MA) 16X8; 9000 rpm; 7,4 kg pull
3-blade (MA) 16X10; 8200 rpm; 8,2 kg pull
2-blade (xoar) 18X6; 8100 rpm; 8,6 kg pull
2-blade (xoar) 18X8: 7300 rpm; 8,3 kg pull
I have the 3-blade MA 16x10 on my ESM Spitfire, but I will try the Fiala 17x8. Maybe that the 18x8 3-blade will work, but probably not. Since I see you come from Sweden, you can find Fiala props at www.aircpro.com.
Another thing to remember with the OS-200S is that it do not like RPM:s above 8400, it is the exhaust-valve-spring that is to weak. You will know that if the engine runs great on the ground, but "bludders" in the air, when you pass the magic rpm:s. In that case you have to get an intake-valve-spring (it is harder) and put it on the exhaust. There where Per Olof Linder in Sweden who discovered the error and the fix. I have tried it on mine and it works great.