I have scanned a lot of backglasses and playfields with the HP4600.
300 dpi is all that is needed to get excellent results
Save and edit in .tiff format
Overlap is very important I have found. With my experience I found that more overlap means better stitching. I now do at least 25% (visual judge) or more overlap.
I use Photoshop Elements for stitching. The PhotoMerge command. Makes perfect playfield and backglass stitches, no moving things around after.
Again: It is the amount of overlap that affects the accuracy of the stitch. I don't have to adjust my first stitch because I use a lot of overlap.
Banding seems to show up on backglasses more than anywhere else for me. Since I redraw/edit just about 100% of the scan to make it sharp the banding just disappears.
Overlap and graphic editing are my two main points.
Alan
4600 (resized).JPG