Buy 5 yards of Momentum fabric from AYCE at Thru-hiker, and 3 yards of Momentum XP 2.5 ounce basis weight.
Fold the momentum in half widthwise, shiny side up, and lay it out on a freshly made bed. The fold will be the top of the quilt.
Lay the Insulation on the momentum matching the top of the insulation to the top of the momentum. Fold the bottom of the insulation up until the bottom of the momentum is even with the fold of the insulation. This will give you a double layer of insulation in the footbox, something I really like on cool evenings.
Use Clothes pins every couple of inches to put the two materials together, then carefully trim the sides from 54 inches at the top to 44 inches at the bottom (or whatever size footbox you want for your overquilt), tapered on both sides. Realign and put the pins back in place as you go to keep everything straight.
Round the edges a bit.
Setting up your sewing machine is the toughest part of the whole process, so make sure you practice on scrap first.
Starting 12 inches from the edge of the bottom, with the insulation on top, sew around the entire quilt, stopping 12 inches from the other side, leaving about a half inch of material around the edges, and a gap in the sewing in the bottom center of the quilt.
Reaching inside the bottom of the quilt, in between the two layers of momentum, turn everything inside out, then tuck and sew the bottom opening closed.
Fold the top edge of the quilt down an inch and sew along the edge, creating a drawstring channel. This area will end up with about 4 layers of material, plus a bit of the insulation, in the seam, making it stronger for your drawcord channel.
Lay the quilt out with the drawstring channel up, then fold the quilt in half lengthwise, keeping the drawstring channel inside the quilt. Sew the 2 folded layers of the quilt together at the bottom along the bottom and about 18 inches up from the bottom twords the top of the quilt.
Then turn the quilt sideways and sew a bartack in about a quarter of an inch at the end of the seam you just finished sewing. The bartack will take the stress off the seam when your putting your feet in and out of the quilt.
Turn the footbox you just finished inside out, so that the seam is inside the footbox, and using a safety pin through the end of whatever cord you've decided to use for a drawstring, and feed the safety pin through the drawstring channel, leave about 4 inches of cord on each end, then trim the cord, put a cordlock on each side, then tie an overhand knot in each end of the cord to hold the cordlocks in place.
Use a lighter and melt the end of the cord on each end to keep it from unraveling.
Enjoy your new quilt but don't stuff it too small. I would suggest that you take a mylar turkey roasting bag, stuff the quilt into it, then stuff it into the bottom of your pack with the opening of the bag folded loosely downwards.
The quilt will compress to whatever size it needs to given the rest of the stuff in your pack.
This will give you a minimum of a 50 degree quilt at about 12 oz or so.