Hey propbuster, I had similar problems on other planes especially at WOT which was solved by dialing in a little more down thurst on the engine. I have found that more down thrust is often needed on a high wing plane, especially if you have it overpowered from the plan specs.

I would think that if it were tail heavy you would have real control problems other than a need to climb. Adjusting the CG too far forward to correct it will probably lead to a crash when the motor quits. First check balance and put the CG about where the plans call for. Then double-check to make sure you have built the wing and the horiz stab at the proper incidences. If these are correct, try adding one washer at a time between the engine mount and the firewall to tilt the engine down a little.