I didn’t choose the freehub, it came with the project bike (early 1980s Araya Road 821), and I won’t swap out the hubs and wheels as they are very nice. Good point about grinding off the gear teeth! I’m doing a full restoration on the Araya Road 821, but thought also that it would be a good candidate for a single speed so wanted to try that out. If I can’t find a solution, I’ll just restore it to 12-speed. So, looks like I’ve got to figure out if there is any non-cycling lock ring that would work in this specific situation. Again, any suggestions greatly appreciated.