I have a Casco Viper, which has survived a major off which saw me a week in hospital and several head to ground impacts which I reckon may have seen me getting a dental bill or at least some facial injuries.
It's very light,I never remove the chinguard. Ventilation is pretty good when travelling downhill anyway, I strap it to the bars uphill.
It's looking a bit shabby internally, so as I'm sold on the full-face thing I will be looking for a replacement. I like the venting of the parachute but if I can find a light, well vented full facer, without removable chin guard I'll be having it. If not it'll just be a new Casco