Hey I'm new here and never owned anything from Iron Heart.  I love this jacket after I tried the N1 from Orvis but it was baggy as hell.  I checked out the sizing but unsure if I should go with a S or M.  I am 5 '7"  155 lbs with an athletic build.  After reading this whole thread it sounds like a great fit.  Does it run on the slimmer side?  Thanks for any feedback before I order.