Andrew,
I understand that you can use the old spools on the new Saltigas, but not the other way round! The SOM spool has the same capacity as the original saltiga 4500.
The Old model 5000 spool fits onto the larger body Saltigas (not the 4500)........ jibbed again.
Not much joy there at all, maybe you will just have to drop a line class!
Cheers Peter.