Yeah, i have tried a Balaclava under my Bell Helmet as well, but it must just be a bit too thick. Between fitting snug and making the under chin strap difficult to clasp closed, it's super inconvenient and ill-fitting. Maybe i'll try to find a thinner balaclava before getting a new helmet. I am gonna see if i can find a store that carries Bern helmets in my area to go test out the fit/warmth.