Same thing here Benny,
When the ballcap says "one size fits all", I get suspicious. When the old high school football team got fitted out with new uniforms and helmets, I had to wear an old Roosevelt era size 8 helmet. I broke down and special ordered a felt (western, not m/c) hat from Billings five years ago.
I've worn helmets for years that I could get on OK, but last year finally special ordered one that actually fit correctly (size/shape). It's a 3/4 and not full face. Don't know much about the full-face market, but the mfrs others listed are reputable. If your spending the dollars, be patient and find one that really fits. You'll be happy.
john
..a friend of mine says it's Danish genes in the pool, as her husband and brother in law all have extra large mellons. I have a few Danish genes rattlin' around, maybe there's something to it?