Hi again, Arno
What you can do tho remove the yellowness: get some water sanding paper with a mark 1000 on it (so its very smooth) and then sand the whole bottom with it, pooring water on the board and then sand the wetted surface until it gets white. Don't sand it in circles, only forward and back, don't sand the sticker and remember to use a lot of water because it's important that the surface is wett. Do leave some color on though...
I hope that you know what i was talking about...
Lampi