I was in a similar situation earlier this year. I was on a ticket that took me from Australia to USA, Europe, Africa and back home on a mixture of UA, LH and QF, although not a round the world ticket. The ticket was issued by LH in Australia. Only the AUS-USA-Europe segments said PC. Internal Europe flights, as well as Europe-Africa-Australia all said 20kg. LH in Australia said that that's what I was entitled to as it wasn't a RTW fare, it was 2 one way fares put together. When I got to New York, I called up LH, and the agent saw the routing, and I told her most of my ticket says 20kg. She told me it was a mistake, and put a note into my PNR, that I should be allowed PC the whole way through. It worked a charm, even for QF!

goodo