Choose a larger size
I purchased it along with the Zip-In Zip. I tried on several combinations of sizes to figure out what would work best, and decided on size L to wear layers underneath, but for the Zip-In Zip I went with size M. The L size is a bit large, but it can be adjusted at the wrists and waist, so it's not a big deal. Anyway, it keeps the wind out, so I can manage quite well even in very cold places.