So the wife and I spent an afternoon recovering the down out of the old sleeping bag I had as it was just "too much" to really use easily as-is...
So we recovered about 29.5oz from this bag, quick and dirty volume to weight test told me it was at least 800fp down, not one feather in the entire bag, I was impressed!
We set out to make 2 underquilts out of this salvaged down, the first being a nice and puffy winter quilt for me that the wife could use during the rest of the year. She's a cold sleeper, I'm a hot sleeper, and she wont camp when its below 40, so no need for 2 winter quilts, yay! The other quilt will be a lighter quilt to use up the rest of the down, yet to be made.
I used the calculator from this site to figure out my baffles and fabric sizes, many thanks to Metor and others for putting that together. For the differential cut I needed slightly wider fabric than I had, so we just sewed 2 panels on each edge to get to the right length, those 2 panels were for the edge baffles, it came out looking sharp with the white fabric trim. We used a heavier ripstop as it was what we had local, and the extra few ounces would not kill us as we are mainly car campers, short hikes. I figured the heavier ripstop would help with the wind a bit too.
60"x48" - 3.5" Baffles - 18oz 800fp+ down - 2lbs with suspension
Black inside, Gray outside with white for the last baffles. Matching white Triangle thingies for suspension. It lofts up huge and stuffs pretty small for the heavier ripstop.
I got in and adjusted everything, and just laying in there without any top insulation at all in shorts and t-shirt it was getting nice and toasty. It was bout 50f with 5mph or so breeze. Can't wait to get out and test it!
We couldn't have made it without all the great information here on the forums and everyone's willingness to share information, big thanks!