Xj900 31a clutch boss image wanted.

Over the years I've collected a lot of parts and even purchased a complete xj900 clutch from a wrecker.

In the parts diagrams the 3 main parts,
Hub
Boss
Pressure plate
Are all prefixed with the same code.
31a or 58l on xj900 (854 or 892cc)
5g2 on xj750

All my XJ900 clutches have a 5g2 stamped boss but 31a stamped hub and pressure plate.

Replaced the pressure plate with a 5g2 and now it works without slipping.

Long story but after much comparison and measuring I realised the 31a hub must be funky considering the specs.

Visually it looks bigger than the 750 clutch yet it takes 7 plates and the 750 takes 8.

So, these are the pics I have taken of the difference between the hub and the pressure plates.
31a on right, 5g2 on left.

The space for plates is 5mm or so larger if the 31a pressure plate is used on the 5g2 hub.

I'd love to see an image of the 31a boss against a 5g2 boss... Just because I can't understand how it could take less plates lol.

 

Ack, transposed the word hub and boss a couple of times.
Sorry if that confuses the explanation.
It is all about the boss, my interest, that is.
Thanks.