I owned one of these early cassette hubs. The Uniglide (only) 6-speed freehub was a pressed-on fit, and I wanted to upgrade the wheel to 9-speed Hyperglide. The hole in the freehub was just a bit too small to be pressed onto the hub shell, so I carefully filed the 'protrusion' on the shell, overall reducing its diameter by less than 1mm. The 'protrusion', like the rest of the hub shell is soft aluminum, so the work went quickly. Of course, the new hub configuration was spaced to 130mm, so a new longer axle and spacers were required.

After that, the freehub pressed on nicely, and then I rode that wheel for who knows how many miles. After a few years, the fit between the freehub and the 'protrusion' became a little loose, so a deep clean of the freehub/hub interface and some red Loctite fixed that.