I just purchased a Shoei X11 Bostrom helmet.
I tried on several Arai helmets. The Vector fit ok, the profile was a little tight in places and a RX7(?) Tommy Gun fit ok but the liner didn't cover as well as I hoped. This led to a seam rubbing my forehead.
I tried on the RF1000 and it fit ok, but the cheek pads were tight.The overall fit was ok except my chin stuck out at the bottom. So I tried on an X11 and all was well in the world until I saw the price tag. $659 was outrageous. I bought one off EBAY on a closeout for $399.99 plus $17 for shipping.
I am looking forward to wearing my new X11s light weight and no wind drag. You really have to try on as many different helmet models and sizes as you can to get the one helmet that will fit your head and feel comfortable.
I tried on a Scorpion EXO700 and it fit really snug all around my head. I think somewhere in between the two Shoei helemts for fit. It was a good decent helmet but is a little heavy.
Do some research and find on that does wind tunnel testing of craetes a helmet that cuts through the wind. With the CBRs you will need a helmet that doesn't push your head around in the wind.