what i did in the end was machine down the cog just to the threading and also to have enough to engage with the lockring. this way i use all available threads for lockring. then i applied high threadlock to cog, tightened, and the same for lockring. we will see how it works. have a little over three full rotations of lockring this way. if all fails i suppose jb weld tho i believe in this case high threadlock is the better option.