Terbob, are you sure you have the measurment correct? Mine has 3-1/4 inch rubber wheels. There shouldn't be a problem with yours. I am using the same battery and it sits just behind the fuel tank. If you really have to add that much weight there are a few things you can do without adding lead. For one, you can install a larger (like 2.5 to 3inch) aluminum spinner along with an apc prop ( for you about a 10-6) and add about 3 ounces. You can also add an aluminum engine mount and add an ounce.