?????????????????????????? Me too!! Yes, spraying or painting will throw the prop off balance. Mater of fact I use clear lacquer to balance my props quite often, depending on how you did it the prop could have been way out of balance!! You mentioned twisting screws, now you can also be way out of tune too. You first tune the top end, bring it up to full rpm then back it down 300 to 500 RPM, now you adjust the low end so you can get the RPM down to what the manual states as the low end RPM, usually around 2000. Just because the engine can pull your plane around at idle doesn't mean it's an engine problem. When I have an idle set on a plane and it's getting pulled I will put a bit of tension on the wheels using fuel line, a washer and my wheel collar.