Originally Posted by Duragrouch

With freewheel, maybe. With cassette, I wouldn't try to space the cassette out at all; I wanted to do that because my chain would sometimes jam hard between the small cog and dropout, so I wanted to make that gap smaller, and put a spacer behind the cassette, however that greatly reduced the engagement of the threaded lockring, and small cog on the freehub shoulders, enough that I did not feel things were sound, so removed the spacer immediately without riding it that way. I looked online, no one seems to make a lockring with longer thread engagement. And changing the rear derailleur from the inferior Dahon compact design to a normal RD and mounting location, cured the chain dropping off the small cog.