I can't remember who it was that posted up their how to on pillar tillering but I want to thank them. I got a bow to brace height yesterday WAY quicker than using the long string and tree. Much easier to get an even tiller too.
My posts are 10 inches high btw. The longer clamp you use the high posts can be. But you could, in theory get away with maybe just 8 inches. I haven't experiment with shorter posts yet.