I agree. I've had awful luck Y->C - LH agents just seem to ignore the certs altogether. I've had flights where I did all the right things, requested it nicely, asked again at the gate, was told to wait and see, was told Biz was completely full, get on board and Biz is empty, ask the supervisor working the flight who is on the plane, am told to go get the cert from my bag, when I return with the cert the supervisor closes the door in my face. Great service, LH. (By the way, in this case I was on a C fare, trying to upgrade my uncle who was on a B fare )

I only will upgrade on LH if I can confirm it, with miles, in advance. The paper SWU route is just too much of a pain. I'll carry a few paper miles certs as well, but that's only worked once when not confirmed in advance.