Scanner is no good for backglass anyways as the art sits 1/8" below the scanner -- it's on the back of the glass. I had a backglass photographed with a high resolution camera and it turned out great. Photoshop has information on different lenses and can correct barrel distortion.
My 4670 also has banding, but I redraw the art for stencils so it doesn't matter too much to me.