When I bought my CX4 with a 2180cc VW it had a Tennessee 54x46 prop. I was never favorably impressed by its performance. It would not turn up and the airplane was slower than comparable airplanes. I broke that prop so that took care of that problem. Recently I have been running a borrowed Sensenich 54x44 prop designed for the Sonex. The 54x44 performed well but the engine had to spin up to generate any thrust. I own a Sensenich 60x44 propeller. I hadn't flown with it because when I first installed it, static rpm was only 2600 RPM. Since I got the engine pretty well dialed in while I was running the 54x44, I tried the 60x44 again a few days ago. It now turns 2900 RPM static and I have two flights on it. I didn't have good numbers for climb with the 54x44 but I can't really tell any difference. Initial climb was about 700 FPM at 3390 RPM with the 54x44 and it still is about 700 FPM at 2900 RPM with the 60x44. I did a speed run at an estimated density altitude of 7600' today which should be about 75% power. Wide open throttle gave 3200 RPM and 130 MPH IAS. The 54x44 had to turn about 3600 RPM to reach that speed. The biggest difference is how much more thrust the 60" prop makes at lower rpms. The props are the same pitch. Speeds are similar with both props but the 60" prop does the same speed at about 400 RPM less. I haven't figured it out yet. Lower RPM means less HP but the numbers don't reflect that. It's a puzzle but that's what keeps this interesting! We will see how it falls out in the long run.