Chuck,
I have mine about 12mm in front of centre of the wing tube and it flys great, these are all a bit touchy on the elevators, I have 12 degs of movement either way on mine and you have to watch the balloning on landing. Having said that they are a very good thing to fly, don't go to far forward as the ballooning will only get worse. Further back in this forum it was gone into quite well and i set mine up from that
Lee