R wrote a review of Stoic Stash Shell - Men's on March 22, 2013
I usually wear a large in most other brand's jackets. I ordered the green shell in XL and it fits really well. I am 5'9", 200 lbs. I tried it on with an Under Armour Cold Gear shirt and a North Face Denali Fleece and it fits really well.
The hood is perfect and fits over a ski helmet with no problems whatsoever; which is awesome for snowy or rainy days! I have to wait and see how waterproof it is. Otherwise, I am very happy with the purchase. It does fit on the tighter side, so order a size up - unless you are super skinny. The sleeves are long, but it does not matter much.
It would be hard to fit more than 1 heavy fleece and 1 or 2 long sleeve baselayers, but that's all a shell is used for anyway. I put it on over an insulated jacket to see if it fits over and it does. I just looked like a marshmallow though lol.
It's very soft and not too loud either like other gore-tex type shells, so that's cool. It could fit into a backpack extremely easily as it is super light. The inside pocket is super small by the way.
I am using it this weekend, so I will post back on how it holds up in 28-35 degree weather.