Does anyone know any good winter helmet options? i cant seem to fit anything thicker than the thinnest hat underneath my Bell helmet.

I've seen Bern and their snowboard-driven line. Anyone have one of these? Ever try one out? I was considering one last year, but was disappointed by the idea of not being abel to wear in summer heat (due to lack of good ventilation. But the more I am hoping to ride all winter long, the more this is looking like a great option.

Any idea would be greatly appreciated.