Well you may want to check the tuning of yours. I live at 6000 Ft and swing a 18x8 APC at over 9000 rpms! Same engine and fuel and plug, etc. I dropped the air density to 21 on thrust hp, and it seems to be more on the ball, but still a little on the optimistic side. I measure around 16lbs and it says like 17, but My thrust measuring technique I think is a little bit off. So it may be pretty close. I will just have to wait to fly my plane.