Since this is not straight forward I was hoping to hear from those of you who have done this before....

We are doing long distance FRA - IAD on LH in eco (W) no problem there
IAD - ANC also eco but on UA all on one and the same PNR

Now come the part I am not sure of - the return is also UA from ANC to IAD but I have been able to upgrade the last big international segment of our flight to business on LH. Now I take it our luggage allownace will only change in Houston when we board the international leg right? Or will UA also allow the higher volume due to the LH segment being the longer of the two and does this major carrier rule come into play?