ORIGINAL: Jim Thomerson
Two things might help (1) move the CG back a half inch or so and retrim. That will make your airplane less likely to climb when you add power. (2) Put down thrust in the engine, maybe as much as 10 degrees. The downthrust will be more effective the more power you apply.
Jim problem is just the opposite, nose comes DOWN whe throttle goes UP, model enter in a soft dive, not climb.