i'd love to see evidence to support .
Agreed. And I am serious, if you have some info please post it and I will utilize it in our safety committee's, ect. we wear helmets with hoods, without, with hoods and mask, ect, ect...
With all due respect, I just don't see it. And the basis for so has several reasons. Mostly revolving around the helmet companies liability, because unfortunately, that's what makes our world turn...I have never seen a warning not to wear anything under a helmet, and the companies would certainly use that as an easy "out", especially since it's a common practice.
If the fit were THAT specific, there would be a more specific fit. It wouldnt be S,M,L,XL...what about those that fall in between. Also my Berns helmet I just got has a winter insert and a sweat band instead of an insert for summer use. The winter one is thicker than my beanie, and because of that the helmet fits a little looser without the insert, but the difference is greater than using my beanie and not using it.