I have a Will Hobby Polecat ARF. 50" WSP with a Magnum XL 46 & Pitts style muffler for power. I have the engine as far back as I can & not destroy the cowl. The " instructions" ( that's what they call them). Shows 85mm which converts to 3& 3/8 inches. Being this is a mid-wing, do I balance it right side up like a high wing or inverted? I know I need it to be slightly nose down when balanced. I have tried both & came out with different weight needed. I have taped 2 batteries almost at the tail before it wants to have the " nose down attitude. Seems like an awful lot of wieght for a small plane. I am NOT an advanced pilot & I know if I don't get it right I'll crash.. Any help will be appriciated. All electronics are mounted behind the CG line.