In reply to flaneur:
To fit in this thing you should either be naturally thick built over chest and shoulders or do a lot of bench press and preferably sport a tummy. Envision american army guy.
Even when I was somewhat flabby at 95kg, the Nano Vest in L was too big over the stomach. Ill fitting, warm leaking? Yes! Slim fit? No!
I still use it though, so its not a disaster and maybe its the leakage which makes it usable for me, I run hot.