Mr.Mugen is right about putting the weight in the wing. It is designed to take all the stress of manuvers, the stab isn't. It won't take much weight in the end of a wing to take care of any imbalance. I always predrill the hole & put a little Med. CA on a finish nail &quickly slide it in flush. On the front to back balance you might try moving your motor back as far as you can. you will be suprised how much difference that can make. Even if you have to trim your cowl some (a big pain) it will definitly be worth it. Every ounce of "dead weight" you put on your plane will effect the performance !! Good Luck