DAMN, thats a lot of dead weight! Have you tried moving the battery just behind the firewall too? You can also add a spinner weight nut made for balancing. I think you can gain up to 2 oz right on the nose which would give a good moment and it can be hidden under the actual spinner. The review of the kit says "Do not use the CG or control settings in the manual; use the recommendations in the supplemental sheet instead".