A couple more comments to this old post.
FNA helmets come with about 1" strips of foam padding on the helmet, one front to back in on the top of the head, two at about 45 degrees on the upper sides of the head, and a strip along the circumference. What this does is leaves a significant area with no foam in the gaps. In my opinion this is VERY BAD. IF only 60% of your head is in contact with the foam, when you take a head hit, the force is concentrated into the foamed area and can not dissipate over the entire head. This results in you getting your bell rung, and a higher potential for concussion or worse.
I got a J3 plaboat helmet liner that is head shaped to cover the entire head, not just part of it. I put this one in my FNA helmet and it is noticeably better with respect to taking shots and transmitting energy into the wearers head.
As a public safety announcement, I would recommend that all FNA helmet users outfit the foam in the helmets to fill in the gaps that come with original outfitting. I know a boater who was wearing an FNA that got a monster concussion after taking a rock shot, and I can't help but think that part of it was the concentrated force on the partially foamed helmet.
With that said, I still like my FNA helmet, you just have to do some outfitting on it yourself. When I got mine, the sweet full face was not on the market. For the money, I think thats the best full face on the market currently.
Having good temple, jaw, and nose protection is a good thing. My thought is that those three are knockout buttons if you take a headshot.