I have a jumpsuit on my 2018 Make Nine list, a copy of this Madewell one. Before I cut into the good Kaufman twill (in that brick brown that’s sold out everywhere) I wanted to check the pattern. So I got a duvet cover at IKEA during their January sale, cut apart the front and back, and used one piece to make a wearable muslin.
This was fast and easy and fit pretty well with minimal tweaks. The waist has an elastic casing as drafted; I tried it with the blousing but thought it made it look dated, so I ended up just folding the casing over on itself and topstitching it like it was an intentional waist detail. It works!
When I make it in the “real” fabric I’ll have to figure out how to do a swayback adjustment, but otherwise I think this is a good fit. Jumpsuits are so comfortable, guys–you’re covered up and look fashionable but it feels like you’re not even wearing pants. Yay loose clothing!