Thanks for your replies. There is a 15-year Old Bikeforums Thread (fixed gear/ road hub- no lockring?) where someone had a similar problem and reading through it, I couldn't come to a conclusion on whether you could get away with skipping a locking. [MENTION=44824]mihlbach[/MENTION], the rota fix method looks like it will work and with a bit more torque than I'd get with a chain whip, but looks like it might be rough on the bb finish. [MENTION=471203]seamuis[/MENTION] yes, it's a multispeed freewheel hub and yep, that's why the improvised BB lock ring. The ring leaves only a couple threads exposed when cranked on tight (photo below). In the old thread, someone said the Sheldon Brown website had info on cog dimensions. I only found it on the second trip to the site after scrolling down (Sheldon Brown- Chainline). Maybe a pre-2005 Surley would work, but I'm not sure where I could get one to try. I'll go with thread locker blue and avoid skids. [MENTION=251447]ThermionicScott[/MENTION], the hub is a late-model multispeed freewheel, maybe the older ones are threaded to the end. If the fixed gear experiment goes well, I'll build a proper wheel and use a frame without a derailleur hanger.

Thanks for your recommendations. Rota fix with thread locker and no skids.