You'll just have to set it up and start dialing it in, because every rig is different. I've seen the mega mid work on boats of various sizes, one friend created 'outriggers' for his 14 footer cuz the mid was a little large. I bet it works well on the 16 footer.
Best rig I've seen to date was a VE-25 rainfly that happened to have its mini d-rings correspond and connect (carabiners) with those on the 18 foot raft, then he just popped up a bar umbrella (sturdy type, not the crap we usually see in river umbrellas) right in the middle of the cockpit. Made for a tight and wind resistant fit all the way around the perimeter with plenty of headroom. Perhaps a smaller rainfly would work on the 16 footer.