Ya, I had to add 6 pieces of aluminum bars that are used to slide into the bottom of fabric louver curtains under the fuel tank. I am guessing they add up to around 7 oz. The good thing is theres lots of room in there so I taped them together with electrical tape and then used rubber bands to hold foam around the weights. Stuffed the weights in and then added more foam behind it to keep them from moving around. I forgot to mention that I also had to open up the covering on one wing to add about 1 1/2 oz. of weight to lateral balance. I can't remember which side off hand. I checked the tank that came with the kit and it hold 15 oz. of fuel. Checked it after an 8 minute flight and I had a touch under a half tank left which will give me lots of reserve even after 10 minutes. [8D]