Pauls advise might be helpful?
If not, I do not fit these springs but a special tool exists, it is a cutted clutch drum which makes it easy to fit the springs.
One of our German guys use an other system. He drills one more hole in two teeth of the plates at the right place and fixes the plates with the right pretension with a small wire using the new holes. Having mounted the drum he pulls out the wire- thats how I understood his system. Have a look to the laverda register forum...
good luck