Hasn't there been instances where a play develops in the cog after a while? I havent' had that happen, but I noticed that the miche cogs wears out a lot faster than the EAI i run with right now. (same drivetrain)
Also, wihtout the lock ring I dont see how the cog would stay on other than the tension from the chain. Anything less that completely taught would eventually pull the cog out of the carrier wouldn't it?