Ok. So I've done a couple of rides now starting at 5am and 7degC. I'd wear a base vest, edge 2, but id still need thermal arm warmers. Overall very comfy and warm enough as long as it doesnt get below 7.
Fits on the loose side but doesn't slip down if pulled up high. I've been using this during the Sydney winter, 7degC at 5am. Great functionality when used with the long compression sox. I'm usually a large in shorts and bought a large.