I would not consider riding brakeless without a lockring but i am somewhat robust around the waist. I think weight plays a significant role in whether this is a good/safe idea. When I install cogs for folks I really tighten them down hard with a foot and a half long chainwhip. I dont think most people out there have the strength in their legs to loosen the cog. The lockring is there as a safety mechanism. "Sideshow" from Minneapolis came to Toronto a few years back for the NACCC'S and rode...Won!... our scavenger hunt alleycat on a brakeless lockring less track bike...so it can be done safely. Mind you the guy weighed like 135 with a sweat on.