I will attempt to clarify some misnomers about how composites and plastics work into helmet design.
A quick back ground of my credentials if it matters to anybody. I have a B.S. in Physics and a graduate degree in Aerospace Engineering-spacecraft design. I worked for a few years doing materials research in both composite materials and UHMW plastics. Worked for NASA for 4 years before coming back to Boulder where I currently work aerospace projects. Not that Im the final word on this stuff, but I have spent a lot of time looking at the physics of composite materials.
So first if I wanted to protect my head from angry fishermen and landowners with guns I would want a bullet proof Kevlar helmet. Kevlar was designed for bullet proof vests where it works great and it his been used well in some other limited applications too. Kevlar is tough next to say carbon fiber, but not as tough as some good plastics. A good plastic is amazing for toughness, which I regard as energy dissipation in the material. There are lots of types of plastics on the market some great and some very poor. It can be hard with just your eye to tell the difference. The plastic Surlyn is a fantastic plastic that is very tough, which is used as the outer shell for WRSI helmets.
I see so much miss use of Kevlar and Carbon in sports applications it makes me sick. I would guess that over 90% of the sports products using carbon fiber is for marketing rather then making the product better. Composites are very difficult to design for the specific application, very difficult and if not done right it makes the product worse.
I think the grateful heads helmets that use Kevlar are good helmets, not great but good. Also very expensive! There appears to be no real engineering into these helmets in my opinion (Others might disagree and thats okay). They have made an extremely strong helmet, to strong for a helmet. They seem to have turned what was once a plastic helmet and replaced the plastic with Kevlar and called it a better helmet for the only reason the Kevlar is stronger than plastic
So ideally this is what I would like a helmet to do. Say a rock hits my helmet while im upside down before I get a chance to roll. I dont want that load imparted on my head be enough to knock me unconscious preventing me from rolling back up....period. If Im unconscious I cant roll up, bad things can happen after that. So if for example a 50 lb force hits my helmet over a square inch the helmet sees 50psi on the outer surface of the helmet. The idea of the helmet is to dissipate that load over a larger area before reaching my skull. So rather then 50lb over a square inch I would prefer 50lb over maybe 25 square inches if the helmet is good. My head doesnt feel 50 psi but rather 50lb/25in^2=2psi which prevents me from getting knocked out.(numbers are just a guess)
So the engineering of a good helmet starts with defining boundaries such as possible forces the helmet might see. Am I worried about bullets? Not really. A car driving over my head? No. The upper end forces would be something like from a blunt hit with a magnitude less then would snap my head off. I dont know what it is 50psi, 100psi 200psi maybe? I feel at a guess it would be less then 1000psi because at some point I could care less if the helmet is intact and my head is detached from my body. This is an engineering approach compared to saying because it can withstand a car running over it will be a good whitewater helmet.
So I do feel the design of the WRSI at first glance is a much better way of distributing loads of reasonable forces one might encounter from a rock while going down a difficult whitewater run. The sandwich type construction used in the WRSI helmet that uses two layers with high density foam in-between the layers I think is an excellent approach to dissipating blunt forces. But I would like to see some actual tests done on the helmet to show its been optimized. I will point out that I think the design approach is very good, actual test data would be needed to further prove the design meets its design goals.
Sorry for the long ramble, just wanting to clear things up a little rather then have some misconceptions from the above posts about what looks like will be a great helmet.
I would be happy to go in with somebody on a pack of 10. I could take two helmets at $35 a pop. Anybody want a Grateful Heads Hard Hit for $70
Hope I helped