I've only owned RF 3.0-4.x. The thing about RF that I've noticed is REALLY BAD... ENGINE PERFORMANCE. Since when does an OS 46FX run in the 15,000 RPM range with an 11x7 APC? or a GAS Motor run in the 20,000-30,000 RPM range with any prop? No wonder some of the planes are such speed demons. General flight physics of the airplanes seems good compared to the 12 I've owned and flown, except for the engines. I'm thinking of using another sim because of this. I have to do some research to find out about the engine performance on a couple of the other sims since the average person doesn't think about that parameter the sims.