I went back and looked at my notes from the planes the kids built. Average weight ready to fly without fuel and Thunder Tiger GP 25 engine was 4lbs 4oz. All took a little weight up front to balance 1/4-1/2 ounce. Now we bought the kits in bulk and could assume they were from the same production runs so we may have had a more consistent average weight that way, I don't know really. In any case <font size="2" color="#00265e">w8ye</font> has good advise, stick to the plans.