I tried a bunch of X428Ps, X430As X427s cut to different shapes and sizes and had good luck with many, my best was probably a thin X427 at near stock diameter, but with extreme tongue and back cutting to reduce the load. Even better than that though was an almost stock Graupner 2318.26. That ws all before CNC props were available, but the Graupners have been proven more efficient than metal props, even when the blade shapes are copies of the Graupner's.
I know the M2 thread is a bit of a PITA, but I would recommend you check one out.