My solution to the problem of wind chilling the crotch is simple and effective. If it is not cold enough to warrant an extra layer on the legs, but cold enough to numb the crotch from excess wind, i shove a knit stocking cap underneath my tights covering my crotch. Keeps the area warm, doesn't put any extra layers where they aren't needed, and is easily removable if conditions change or you get too warm going uphill. Been using this trick for years.