I have a SP Club Pro that I use in the spring and fall. It doesn't breathe well enough to layer under it. But it rolls up small and is perfect for taking along----just in case.

I have a have a Transit for winter and heavy rain use. It has far more ventilation and an ass flap that is very nice when in heavier rains. I can layer two or three levels under the Transit and have never been cold in it....but, I do live in Georgia