I haven't tried it yet Red, just in the planning stage.....in other words I was mulling it over and probably didn't explain myself very well, so will try again.
If you can imagine drawing a square on the circle, the lines will be your stitching lines when you place two completed circles together...
Well if you make the batting 1/4" bigger than this square then when you stitch each circle together you will catch the wadding...OR maybe do the central quilting first before you join each circle and then you can just make it the size of the square....rambling again sorry :D