I would NEVER take out quilting (no perfectionism in my wiring <g>) ... but, I am wondering if the reason there is so much puckering is because you put too much quilting into the quilt?
And, I don't know if it makes a difference, but there is a stretchy side/direction of the fleece and one that is more stable. If you happened to put it into a frame with the stretch in the wrong position, it might make a difference in the way the quilting was affected.
If you did a simple stitch in the ditch, were you using a walking foot? ... Perhaps a bigger stitch, longer stitch would have helped avoid the puckers?
Am just trying to figure it out because I read another thread about using fleece as a backing, and I am seriously considering making the switch. <wave>