I've been real happy with my Bell M2 so far. It has a larger viewport than most SA rated helmets, but not quite as large as M rated helmets. On autox courses, I can't say that I've had any visibility issues. Bought it from a local shop outside of DC.
I ride motorcycles and am fairly confident that the same principles would apply to helmet fit.
Arai and Shoei are probably the top 2 helmet manufacturers. Arai has more options for fit. The Quantum and RX77 fit round heads. The Signet series fits oval heads. And they just added a line for all the heads in between!
The best price I have found on helmets is:
Fit is by far more important than style or graphics. It's your head and your brain, don't cut corners by buying a poor fitting helmet. They have saved my life on 2 occasions.
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