I'm running a handful of OS91s in my warbirds. Every one has a MA14x7 three blade on it now and it's a match made in heaven.

However, every one also has the airflow through the cowl controlled with baffles and the position of the hot air exhaust holes. Block the entering air except in front of the engine. Make sure most of the exit area behind what you want to cool. Consider whether the exit is in a positive or negative pressure area. If you can see the exit hole from the front, it's probably in a positive pressure area and just might not work as well as you expect.