I just finished my wife's birthday present! (even if I finished it the day after). I wanted a double quilt instead of always packing 2 sleeping bags for us, and I am hoping the dimensions will work. It ended up being 70" wide down to the footbox (footbox 17w x 10h), and 78" tall. I used 900 fill down and momentum fabric from Thru-hiker (the down was impressive) Thanks Thru-hiker.
My wife sleeps much colder than I do, so I made the baffles 3" on half of it and 2.5" on the other half (hopefully I can remember which is the cool side in the field). I sewed them 6" apart.
Here are some pics:
I am getting good loft from the down (over 6" when it is doubled on itself) so I am very happy with it.
I was planning on an oval footbox, but was running out of time (or ran out of time) so I ended up going with a rectangle. Not as pretty, but just as useful.
Fun project. I hope it works good in the field. Thanks to all you MYOG'ers out there for the inspiration!