I have built VW engines for several people in the past and know what props that works on those aircraft. On the SSSC, I talked to Pops, ( died last Dec) at Culver props and gave him all the details about the engine and airframe and the 60"x26" prop was what he recommended. He hit it right on the money, perfect prop. A VW engine would never develop much HP with the rpm it would turn the 68"x 34", to much dia and pitch. The engine would run very hot with the high Manifold Pressure trying to turn the prop. My 60 HP, 1835 cc engine at WOT would turn the prop at 3150 rpm in a climb, static RPM was 2950 and I cruised at 2700 rpm at 80 mph. Fuel burn was 3 gph,. No cylinder head of oil temp problems. Lots of power, take-off in about 250/275'.