I've been hunting for a back for a couple of years, but despite various leads, nothing satisfactory has come along. However, I've had a couple of 3" wide western maple boards in the outside lean-to, and more or less in desperation I tried the template to see if a complete back could be got out of this rather massive lump of wood.
With a little care it could be done. One knot could not be avoided (see later), but a small inlay could take care of this, since the fault was very close to the centre line.