OK, thanks for your impressively quick replies. I have asked over at the LH forum (as I would upgrade with LH miles) if a FRA-IAD-LAX upgrade would be 50k miles or 50+15k miles, but have not received a response as of yet. I would try to upgrade the two flights together, if it can be done with 50k. If it has to be done seperately, I would upgrade only the transcon leg, as 50k seems expensive to me for FRA-IAD only.

Btw, I am continuing from LAX to SAL, so even three or four hours of quality sleep inbetween would be very welcome, and that is why I would choose to upgrade the transcon leg.