My bike was registered Feb 2002, it was one of the challenge bikes so I imagine they all came from the factory at the same time (and it wasn't old stock from a dealer showroom).
I've emailed the ebay vendor (mike - very helpful) and he says Ducati Flywheels had different diameters for that year. I'm going to split the cases and send him the dimensions to check and make sure.
It's never easy is it