Sounds like you should be talking with the troubleshooters at the RTW Desk. As long as you do not change the JNB-HKG segment, your fare can not be recalculated. Changes are allowed to the rest of the ticket for no charge before you start travel. One catch is that if your trip becomes more than 16 segments long you will need to have your tickets handwritten. You can wait till HKG to change your ticket and pay the 75.00. One of the "plusses" of Oneworld is that each member can change the others tickets. CX should not have a problem if you do it there. Also you will have burned off a couple legs making it easier to reissue. And try the AA NRT-MIA. The long hauls are actually good service. Keep us posted at FT.