So far I have been testing with a 8.8x8.75, thought this would be a good standard to test with. Since the start of my testing I have not even been able to crack the 19k mark except at full lean so I figure about 18.5k to give some room to unload. So I figured there must be something wrong concidering I've seen engines that turn this prop about 1000 rpm better(19.4 -19.6k) and still have room to unload. I don't know, maybe the thing is just tired.... It's my first year in 428 so I'll probably just run it until it won't run anymore but it would be nice to at least be in the ball park.