Not enough adjustment

[DaveZ1]

Setting the ignition timing on a Z1B and seem to have ran out of adjustment on the base plate and the points plate to achieve the correct setting.
I think the advancer is from a later bike A4 or 1000 but when adjusting so the points start to open at 5 degrees BTDC on the F mark, I can't move the plates any further and am still a few degrees short of the mark.
1 and 4 can be set within the adjustment slots but 2 and 3 run out of adjustments?
I know the static timing was changed from 5 BTDC to 20 BTDC on later models so even if the advancer is from a later bike ie f mark at 20 BTDC I should still be able to set at this mark. Could the mounting plates be different too?
Any thoughts guys.

[ADRIAN H]

Extend the grooves on the back plate - till it works ?

I am sure early Zeds (Z1, Z1A, Z1B) had a different back plate to later ones Z900 ONWARDS).

[Al]

Has the advance / retard mechanism lost the 'soft pads' form the arms?
If so the advance range will be different from standard and the initially retarded point will be beyond the reach of the slots in the Dyna baseplate.

AL