I mean a shirt, sweater, and insulated jacket can keep me very warm flying down a windy mountain at <-20C so do you really need that many layers?

I’ve done undershirt - overshirt - jacket 1 - jacket 2 in the dead of winter. If the Sun vanished and the temperature plummeted to -100 I’m pretty sure i could figure out how to add a third jacket and then a blanket on top of that.