I agree with everyone. If you have already pur chased the bottom fabric still use it as a type of mattress under you as having plenty of warmth below is very very important.
Enjoy your selves.

And cheaper. -the heavy duty zippers alone will cost a fortune and that's if you can find them. I bought my son's sleeping bag at the Army Surplus store. It was both warm and light weight. I had a couple moving van pads that I sewed together around the outside hem and then one seam across the center length and width. He had plenty of pad under him. He went camping in February and that was up in NW Ohio on the shore line of Lake Erie. Day time temps were only in the 20's -and lord only knows how cold the nights were or the wind chill factor.The Army bag was plenty warm .

Tartan and the others are right, I would just add one small idea. I am too old and arthritic to sleep on a cool ground. I spent less than $100 on an air bed that had its own pump to inflate itself, and I just buy new batteries occasionally. (Never store them with the batteries installed.) Mine is a Queen size, double layer, but a single layer would be just as insulating and possibly leave less bedding to dry each day?) We use a smallish two room tent, (dogs get the other room) and the Queen air bed fits fine. My family teases us about our "Taj Mahal" campsite, but we don't mind as comfort is more important than conformity. You could then use your wonderful thick wool quilt as an extra layer on top if needed...

As you know by now, the monster you want will be almost impossible to dry. How about zipping two sleeping bags together, and sew your wool and sheet to the bottom by just a few stitches by hand in each corner and some in the middle, as if you were safety pinning it together. Do the same for the top layer. When you get back, you will be happy that you can take it apart to wash and dry.

That was my first thought. When we camp, we zip two sleeping bags together and cover us both with an old down comforter. Always toasty and it has gotten down to 35 degrees.