scanning is such an inprecise science that the only way you can tell anything is to
scan disks, preferably high quality burns, with 2 different scanners and hope to duplicate results. The nec 3550/4550 line are too individual in their best scanning speed. I took disks that scanned in the high 90's(MIJ) on my benq 1620 consistently and then found the stable point of scanning for my nec 3550. When I could overlap
the PIF graphs and get the PIF totals to match(within ~10%) then I started to trust my nec 3550 scans at 8x.
3 or 4 different scanners would be better but I never got any consistent results from my nec 3520/40's