I installed the Xoar 15x6 prop last night and did another test run on the engine this morning. All I can say is WOW this prop rocks on the NGH GT17. I am getting a very good idle at 1900rpm and I got 8700RPM on the high end. I think this Xoar 15x6 prop is the one to use on this engine. I hope to get a flight this Friday if the weather holds.