Yes, like Colin said, try shifting the battery or/and receiver to the rear of the fuselage to balance it on the CG. If those fail to make it happen, find out how much needs to be added and cut a small hole in the bottom of the rear sheeting, about the size of a BB pellet and mix some epoxy and bb's in a small cup to the same weight as the amont required. The easiest way to figure that out is to add the BB's to a plastic mixing cup about 1 oz in sixe and place it on the back of the fuse near the tail. When you've reached the proper amount of BB"s, just mix up enough epoxy to get them coated in the cup and insert them through the small hole with the tail pointing down, let them cure in the fuselage and recheck the balance, usually it will require a small adjustment but it will be close. BTW, if you need 4 ounces in the nose to balance the plane, your 1 ounce too heavy in the tail, the reverse of the formula works as well, so 1/4 ounce in the tail means 1 ounce in the nose too much. It almost always is a 4 to 1 ratio.