[QUOTE=Francesco]Does anyone know of a good flatbed scanner that can take up to 12x20 prints? Many thanks in advance.[/QUOTE
I scan 12X20 negatives wtih an Epson 836XL scanner. The 836XL is the immediate predecessor of the current 1640XL and scans at an optical dpi of 800 dpi, in contrast to 1600 dpi for the 1640XL. However, unless you plan to make prints larger than about 24X40" 800 dpi is more than enough for 12X20" negatives.
The scan must be done in two parts and stitched together with Photoshop. Stitching is fairly easy to do once you learn the procedures, and is the only option available for a flatbed scanner.
About two years ago someone made drum scans for me of ten of my 12X20 negatives, at 600 dpi. In my opinion the scans from the flatbed 836XL at 800 dpi are easily equal to, if not superior, to what I got from the drum scans.