Thanks. It was my mistake to think of getting 20 segments on the DONE3- I was thinking of some of our nested tickets(oops).

I got onto Qantas.com and checked out the prices for the trips we need in Australia, and if we buy them online, in discount Y, they are more expensvie than the difference between a DONE3 and 4, so we will do them as part of the DONE4 in business class and save some money

I have been on seatchecker.com to see if D and A class (US domestics) are available, and amazingly, there are a number of seats on all of the flights that I wanted^ No if I could only get the person I am dealing with in CX CMB office to actually reply to my emails (and 2 phone calls...)quickly. I'll try the AA office there I think.

If I book CX830 as the AA codeshare, are the taxes and charges cheaper than using CX?
As an aside, I must say I am glad we are not trying to find 2 A class seats on CX to the US....