Anyone have any tips on sizing? I'm 6', slim/athetic - trying to figure out if I'd be a Medium or Large. It's been a couple years, but last time I was sized for a suit I was around 15.5-16 (neck), 32-33 (arms), 38 (chest) if that helps. I've never had a base layer top, so I'm not sure what the fit should be like. Hoping to get this for snowboarding, as well as backpacking.