It's not just the ARF'S. I have never built a kit that was close to the stated weight on the box. You can't build as light as the kit or ARF is supposed to be without sanding and grinding half of the wood in the plane. I have baby scales that I check at 2 1/2 and 5 pound weight before I check the weight on anything. I use super glue mast of the time and sand everything as much as I can and I have postal scales to weigh and use the lightst components I can get and none of the planes ever come out even close.