So this might be a crazy question, but is there anyway to float the quilt backing too?
Here's the story, I have a new customer that is intent on saving as much of her fabric as possible. Her quilt backing is two widths of fabric sewn together, but she decided not to cut the widths even because one fabric had nearly a half yard more length than she needed. Her idea was that if I started quilting at the top edge of the backing (this edge is even) then stopped quilting whenever I finished, she would be able to cut off the extra and get a larger hunk to save for later than if she cut it even beforehand and then trimmed away any excess after quilting. (I really hope my explanation is making sense, but if not I diagrammed it in the attached image.)
So I'm wondering if there is anyway I can work with this wonky un-square and uneven quilt back? The best idea I had was to partially float the quilt back over the quilt back bar and just be careful to smooth it every time I advance. But I am concerned that this won't hold the tension well. Another idea I had was to sew some muslin to the shorter half to even the back out while I quilt then remove the muslin before returning it. Has anyone tried anything like this, or have any other ideas?