I went from a 1600 nimh pack stuffed under the radio tray to a 720 AAA nimh pack in the tail. I saved over 2 oz total weight, more if ya count the ballast weight i could take off. I cant imagine running a futaba 600 nicad under the fuel tank like they say in the manual. It is realistic to get this plane down to 3 1/2 lbs with the right combination.