Basically the bb lockring doesn't do much, make sure you rotoscope the cog on well and it's as close to safe as you can get without getting a fixed/fixed hub (might as well only get fixed/fixed hubs as free wheels will fit on fixed threads, but the other way isn't really safe)...
The reason everyone says it's fine on the track but not on the road is because if it comes off on the track the worst that will happen is you'll get run over by a bike...
Basically the bb lockring doesn't do much, make sure you rotoscope the cog on well and it's as close to safe as you can get without getting a fixed/fixed hub (might as well only get fixed/fixed hubs as free wheels will fit on fixed threads, but the other way isn't really safe)...
The reason everyone says it's fine on the track but not on the road is because if it comes off on the track the worst that will happen is you'll get run over by a bike...