G'Day,
I wear one in R22/R44 and H269. I fly mostly for private ops.
I have a number of helmets (collector of them) and a few are in flyable condition. SPH3/4/4B and Alpha fit on my head and into the helos without any problem. I am 5"11" and they do not cause me any concern.
My job takes me to the sites of many helo and aircraft accidents and from what I see, I will always wear a helmet when flying.
Tinkicker..........