If you are after torsional stability IGPMP my favorite setup comprises of a leather grip, over grip, rubber band dampener and 10 grams of lead at 3 & 9 (2 layers 5 inch strips). Balance is maintained as most leather grips will add 10 grams of weight to the handle.
Play with the above setup and if you still need some added power or want to raise the sweet spot slightly remove some weight from 3 & 9 and add some weight at 12.
If i remember correctly the setup should raise the swing weight to mid to high 330's and static weight should be around 355-360 grams depending on strings and dampener.
Also strings and tension are important. I really enjoyed a gut/poly hybrid in this frame strung at 53/51.