I've got a 'certificate' too. Also, an appropriate diploma signed by GM and authorized techs and engineers at Saginaw Steering Systems. These credentials are available for anyone to inspect. I will be happy to supply pictures of my diploma. I add this part about availability of my credentials because I've been accused of lying about my experience/credentials here on this site.
Since I have the endorsement of the original equipment manufacturers of the steering components on our cars I'm qualified to inspect replacement parts. With this in mind, a rag joint kit installed properly is an excellent fix for a worn rag joint. I have installed a kit on my own car and it is at least as safe as it was when it was new.