8F was my coldest ride this year. No problem with the crotch. If I ever have an issue down there things are seriously wrong. I tend to run a bit warm.
Clothing:
Cycling shorts
Tights
Jogging pants
I have a pair of poly longjohns I have yet to use. The next time it is cold I may try to fit those under the tights and leave the jogging pants in my panniers. More aero.