Good question Crankpin. I also am considering a Focus Sport build and wondering about power choices. I am almost convinced to go with an OS120AX. I realize that I would have to modify the engine and install a Perry pump or put the fuel tank behind the firewall and live with trim changes. I flew afriends Venus II with a 120 AX and was amased at the throttle response, power, and torque. It seems like a much better 2 stroke than most that are available.