I hear what you're saying, and I have no doubt that you know what you're talking about, but it doesn't all make sense to me (some does, but not all). I agree that in a lawsuit situation, the chemicals of the paint attacking the structural integrity of the helmet would probably be the target of the defense. In the real world, I don't buy it - especially in a situation where the helmet already has a factory-applied layer of UV-resistant paint. If the airbrush paint was attacking the structural integrity of the helmet, I would expect to see signs of irregularity where the new paint was dissolving the factory finish.
As you said, at the 10U level, it's not really a concern (if there is one at all).
I agree with you Eric. There are so many ways for a company to pass liability and/or not honor a warranty. In the end its about money and not exposure.
I would think a helmet or hard hat would become brittle in the painted area if there was a chemical reaction using the sun as a catalyst but they tell me since im not a scientist I cant argue with the scientist and common sense is not a defense