Just out of curiosity, what's the point of a helmet liner in the first place? I've never found that my head gets cold when my helmet is on.
In the winter I can't zip my outer jacket up all the way now with just a heater liner on under it. The neck holes just aren't large enough for those of us with gorilla size necks.
I'm sure it's a great product though if it works for you. There skivies are outstanding.