Interesting. I sized up to a large in the two flannels I ordered from Gustin in order to up the sleeve length (this was a while ago, before there were large or tall fits). Not sure I could've swing a medium, although the body probably would've fit better. Oddly, when I tried a slim large in the workshirt, it was about a size too big everywhere, including the sleeve length. I'll be interested to hear how the slim mediums work out for you. @joshgustin, any plans for a five-panel cap that doesn't have a contrasting brim?