I just got a used Cremina from 1975 and am in the progress of rebuilding it. Mostly I'm trying to follow the advice on the old OE videos and buying the tools needed to follow along.

In the videos Doug suggest that you have something like a half a millimeter between the lever and the cup. When I have the second nut screwed all the way to the bottom, the lever still bottoms out. Is there a solution for this? Any suggestions?

(it's screwed all the way down in the picture, I don't have it pushed all the way down just to show where the nut is better.)

This might sound stupid but once my lever fork used to touch the group head. I discovered that I inadvertently had the lever fork upside down. This might not be your problem but try flipping it over and see what happens.

I'll try it! (once I get the snap ring pliers )

Maybe the pin worn out or the hole in the rod got wider because of force pressure during the machine life time? take it out and take a close look at it.
I bought the snap pliers set from Harbor Freight and sand it as Doug suggests. Works perfect.

Yeah I accidentally got something that looked ok on amazon but was not only way too big but also way too far apart so sanding wouldn't work, so now waiting for another set.

Yeah, the little cheapo snap ring plier set actually works very well for these tiny circlips.

Another way to adjust the piston - works on Creminas and Pavonis - is to use your fingers on the bottom of the piston face to feel when it's just barely above the bottom of the cylinder. It will be maybe a mm above the shower screen in that case. Then you just hold it in that spot, spin the lower nut down to hold the position, and then add the second nut to lock it in.