VFR 750 FG (1986) Suspension Preload Spacer

Hello all, wonder if you can help me out.
Just dismantled the forks, put in Cartridge Emulators & new springs from Race Tech (totally transformed the handling).
However the previous spring was a Hagon progressive & the original Crucible plastic spacer had been cut down which gave an overall preload of 20mm. I have done the same with the new setup, but would like to know if any body knows the actual length of the original crucible spacer. From this I can determine the correct preload (I know what the o/e spring length was including washers).
Many thanks