Hi Albie.
Made it into the garage with a tape measure this afternoon:
The 'Ducati' decal at the back of the seat cowl is 100mm wide.
The cowl is all curves, but the bottom edge of the decal is 30mm up from the rear edge of the cowl, measured centrally using a steel tape with the end of the tape hooked over the edge of the cowl.
This is the original cowl on my '94 m900 with '93 date stamp moulded into the underside and what I believe to be original paint as it still has the supplying dealer's 'Murayama' decals too.