As Jim Thomerson found pitch stability on a free flight is about getting enough but not too much. You want enough to let it recover from a stall or tubulence induced dive but not too much. Too much results in a model that wants to loop under power just as he found. I know it sounds counter to what most RC'ers think but it's been proven successfully by many FF'ers over many years. In fact I've seen far more planes crash during initial powered flights from having the CG too far FORWARD than I have from having it too far back. This applies only to FF models where it's not possible for the pilot to add down trim when things turn nasty.