Vespa variators can be derestricted by removing a limiter collar. This collar limits how far the variator will open. Removing it may give you a bit more variation.
This lip is brass, I think, so it's pretty easy to grind off. I use my bench sander.
After the lip is gone, I clean up the burr with a polishing wheel in my bench grinder. I also clean up the inner cheeks of the pulley to get it back to a nice, even surface. Makes it shiny, too.
Afterward, you may want to consider cutting windows to allow your weights to pop out even further.