thanks to all of the advice. I try to verify all these items.
As a last resort I too have thought of a vintage clips.

Massimo

I've knotted a loop of innertube rubber onto the lower mudguard stay at the pannier welded stud, it is then looped over the foot of the stand. This works a treat, quick to put on or off and if you put it on the near side it doesn't get dirty from the exhaust.
Richard

Hi all,
problem solved :relaxed:
I replaced the spring with a NOS spring (they looks the same) now the stand does not bounce anymore.
Thanks at all!

Massimo