"Why the Duomid and not the Solomid..."
With the Solomid, the sleeper occupies all of the floor area so an inverted V setup is required. With the DuoMid you sleep in the back half of the pyramid, so you can use a single center pole to support the mid (you can slightly offset it to make entry into the inner solo nettent easier). Additional benefits of the DuoMid are that your sleeping area is protected from rain fall when you open the door, and you gain a large vestibule area. The DuoMid is cramped for two, but it's an excellent solo shelter, particularly in sloppy conditions when you need a little space. It's a lot of benefit for 3oz and there's nearly no weight penalty if you'd have to carry two poles to setup the solomid.
My DuoMid is a prototype with a few less features and it weighs 11.6oz. It's such a great haven. Simple, spacious, light and strong.