Some of my aerobatic models have actually ended up with a tiny amount of up thrust. I however am not recommending that to you. The difference here is the airfoil. My race planes have a semi- symmetrical airfoil like your Chippy. I run those at zero/ zero/zero. If you have given it down thrust to compensate for climbing at full throttle your wing to stab incedences are off. Have you measured the airplane yet?