I've done well with a pair of PI Gavia Plus bib tights for the past 3 years. Only in the most extreme of cold that we get up here (below 20F) do I need to double up with a pair of shortie thermals underneath to keep my junk warm. My legs are just fine, though. I've done plently of winter 200k permanents in them without problems.

I'm not sure about skinny fit on their small sizes. All I know is that their 2XL stuff fits my Sasquatch stature really well.