I leave the prop RPM set high as it will not normally get there, and it keeps the turbine on full rpm. If you set it too low and unload the engine in a dive, the max prop RPM will be reached and the turbine can be throttling back.
I think the Biela 25 x 12 TP is a good match, 2 blade larger props will have a high tip speed and put a lot of load on the gearbox. The Raven is so light you won't be short of power. Our's had a 2003 SPT-5 on a 25 x 13 3bl Biela and its vertical forever. We are cool and fat with air, I can see the 24 x 12-3 working in heat.

Dave