krayzc,
No I have not tried the Mejzlik. I have wanted to, but have not been willing to fork out the $'s to experiment. I will be VERY interested to hear your results with the Mejzlik vrs the APC on the OS 1.60. The higher RPM they should turn on the OS vrs the RCS 1.4 might yield different results. Also, If the Mejzlik turns higher RPM than the APC, I might be more interested in a Mejzlik 20x6. I think the OS is happiest in the mid to high 8000 rpm band. The OS specs say peak HP (3.7) at 9000. But I called and they said peak torque is at about 8500. I suspect running a prop above 9000 on the OS is burning excess fuel without appreciable increase in performance. If the OS will spin a Mejzlik 20x6 about 8300 - 8500 rpm, that might be the best prop for 3-D work. Can you get an accurate weight comparison between the APC 18x6W and the Mejzlik 18x6 ? If you don't have a good Digital scale, your local post office will probably weigh them for you.

Also, what fuel, plug, and muffler are you using?

Thanks for your information.