i usually wear Large and the Jetstream was was pretty snug on me but I'm going with it anyway. Arms were good, torso length was shorter than most and belly area was tight but I got some LB's to lose so I think I'll be in good shape. I got two baselayers on under it and felt comfortable, I will only end up wearing one under it anyways and put a puffy on over top if i need more warmth.
I would say most Sitka products run a tad small. I've been using them for 4 yrs now and most of my items are a size larger than my normal wear sizes. I
I am pretty much built the same. I run large in all of my Sitka tops other than my mountain and jetstream vest. I like a more snug fit on my vests. I have two jetstream jackets and the large fits good. I also have two Sitka Kelvin Lites and I run a large and it is a touch big, but I tried on a medium and it is too constricting in the shoulders for me.
I have never thought of Sitka running smaller than normal. I usually wear large and all my large Sitka items have had some extra room for layering. However, I just bought the kelvin active and it was tight in the shoulders and even a little short. Just swapped that one for an XL.
I have a bit more...er...um...power than you folks. I am mostly xxl but go xl sometimes. I have some Sitka tops in each. My decision generally hinges on if I do or don’t want room for layers. My outwear like my kelvin and jetstream are xxl. Some other tops are xl. The kelvin active I have is xl and is the only piece that is a bit too tight in the shoulders and short in the waist.
The large jet stream and kelvin lite hoody fit me fine. The large chugach is a tad big on me. I have a medium 90% jacket and it's tight but I use this as a mid layer so it's fine in my system. I wear a 42 regular suit coat and weigh 180 lbs at 5'11". I think Sitka is true to size for most part.
I've always been a bit of a tweener as well between med/large I'm 5'10" 165. In Sitka i run: L Jetstream, M Jetstream Vest, L Kelvin Lite Hoody, M Kelvin Lite Vest, M Traverse Cold Weather Hoody, M Cloudburst Rain Jacket, L Timberline Jacket, M Mountain Jacket, L Core Midweight/Lightweight, M Core Heavyweight Hoody. Just for references, it is a lot of trial and error. But it also comes down to what your specific uses for each piece might be in your particular layering system as to how you wear each piece.
Does anyone know if they changed the sizing in the jetstream jacket? I used to have one a few years ago and it was a bit tight. I tried on a large sub alpine jetstream this summer and it felt like it was a bit bigger, which was good.
I'm 5'8 and 170. The Mountain jacket seemed small too me. I tried some on a couple weeks ago and I would need and XL in that jacket. A large felt tight in the shoulders.