Make yourself a balancer, your fingertips are too blunt to get a good indication of true balance. Take a piece of wood, say a 12"long 2x4, and two new pencils with erasers, drill two pencil size holes in the wood, 2"wider than the fuselage. Stick the pencils in the holes with the erasers up, mark the spots on the wing where it should balance, and place the plane on the erasers at those marks. Now move the battery pack if you can till the plane sits at a slight nose down attitude. If you can't get balance by moving the battery, add lead weights as others have suggested, as far forward as you can, and wrapped so they can't move around. Good luck.