Joe, if you went from a pull to a tuck then your CG shift was fairly large. Honestly I'm still not getting why your trim is not changing with a CG shift as it does on every airplane I have ever set up. I think it has to do with how the stab is loaded. If you think about it if you are nose heavy then the up trim is going to place a certain amount of load on the stab and has the effect of making the airplane fly heavy. As you move the CG aft, the load decreases as you don't need as much pressure to hold the nose up. That decrease in pressure should directly translate into less elevator trim. If we continue to move the CG aft we get to a point of having almost no load on the stab and that's when the airplane starts to hunt and will not hold a line. I not only apply these techniques to my aerobatic models but my pylon airplanes as well. Typically on all my airplanes I move the CG back until I notice the lack of stability and then move back to where it will hold a constant line without a large amout of correction inputs. Ironically this is the point where I have almost no elevator trim if any at all. With the aerobatic airplanes this will almost eliminate any tuck or pull while in knife edge, a small amout of mix takes care of the rest. On the racers it leads to minimal elevator travel needed to get through the turns. Less travel= less drag= more speed.