I have a Sterba 68X74 , 160HP Lyco on my RV-4, and get about 150kts at 8K, but that's turning 2600 RPM..its definitely a climb prop and I can easily hit 2800 RPM or more. I have Jclarks "old" tried and trued Sterba ,68X76 I'm going to put on to settle my RPMs down at cruise. You will likely see a lot of variance in different brand props with the same diameter/pitch, and I recommend flying your plane for a while and see what your mission is, and go from there. I haven't met many RV folks with FP props that haven't tried at least 2 different ones to find their sweet spot in performance vs efficiency. I flew an RV-4 160HP delivery flight for a friend from Fla to NC with a Sterba 68X76 that couldn't get to 2350 RPM at full throttle yet cruise was around 150Kts. Variations in tach indication, AS indicator accuracy and other factors may hide the truth. Go fly awhile and use calm day GPS ground speeds to give you some comparison.