Now for the other side.  I have odd pieces in varying sizes to work with on the back.  I measured them all, and divided by my 2.25.  That gave me the scale pieces I would need for the graph paper plan.  I cut out pieces of graph paper and put the puzzle together for the back.  I do not have enough to cover the whole back.   Ok, Plan B.

I think I actually like Plan B better!  I am going to cut the leftovers into strips and do this nifty idea.  Meg introduced me to this method, and I used it on some towels, but now it will be done en mass!  I will sew a good size piece of the strips and add  bands of fabric to the top and bottom to get the yardage needed for the back of the duvet.  Actually it will end up being a reversible duvet cover.  He can flip it to which ever side catches his fancy for the day.  Thanks to Plan B!