Yeah, go try some out. To me, helmets are like shoes -- you can't just buy one without trying it on first.

Well, you can, and it might not be as awful for you as a badly-fitting pair of shoes, but there's no substitute for putting it on your head. In my case, I've got this pointy ridge on the top of my skull. If a helmet has anything that touches my head at that spot, I immediately put it back on the shelf and never consider it again.

That's something that I'd never know for sure from just an online store listing.