Before you do any covering with poly U you have to give the plane two coats of sanding sealer to keep it from absorbing into the wood. If you don't it also just wastes the Poly. About 80% of the poly used gasses or drys off so you aren't leaving behind a lot of extra weight. Most the time it's people using too much paint that causes the plane to come out heavy. If you don't want to try glassing then give the Solar Tex covering a thought, it comes in the main colors you want and takes to paint very well.