Like I said im not at sea level, make's all the difference in the world and at one time APC did make a sport 18x6 but its no longer made. Just like the 13x8 is no longer made in the pattern but still made in the sport. Not any of my 160's will turn that prop over maybe 8 K 7600-7800 rings a bell at the most and spool up is slower than cold tar on 15 % nitro. I took it off and used a 16x10 that worked well, then I got the 9 K + your talking about Like I said you can't compair apples to oranges. Try running one of your engines at 4500 to 5000 feet and see what I mean, just try cause thats about all you will do W/O changeing props.
And really I want thrust not RPM's, the two don't always go hand in hand.