Greetings All: I am a newbie to making and or playing flutes, specifically Native American Flutes. I am of recent making one out of 1" PVC and things progressed pretty well even up through tuning until I got to the 6th hole and find it to be rather trickey. It seems to have trickey overblow characteristics on that hole and I am covering only the 4th hole during the tuning of that hole and expect to play an F as this is a tenor flute as far as I know. Any tuning tips would be appreciated or other methods. The hole count begins from a makers point of view counting from the far end "south end" of the flute, not sure if I should mention that or not.