Normally I book my star rtw tickets with a travel agent, but as I have a couple of UA issued star vouchers, United have told me they will have to issue my ticket.
I would like to book my itinerary online to see if at least I could get the extra 1000 miles being offered in Australia.
As a former travel aget I could just book each segment in the correct class of service required, ie B or M...is there a way to do that on UA online?
I can only see to put all the segments in requesting economy and hope it converts it...if not will UA reservations change it to the correct class?
Or should I just let UA book it all direct?

I'm asking this just before I go to bed, hoping that in my morning I will have an answer from various experts. Even those Flyertalkers on the Oz east coast get up 3 hours or more before me

Once upon a time, it was possible for the passenger to book specific classes (remember easysabre?). But now, the airline website cater to travellers who expect to pay only the lowest class offered. So, by and large, the website will always default to the lowest fare class available.

In short, the answer, unfortunately, is no.

I agree that it is not possible, but for an additional reason. Even if you could book the appropriate fare code ("A" for first class and "D" for business class (I don't know what the Star RTW fare code in economy is), an RTW is a different animal and has to be priced indepently of the fare code. There are "D" fares that are not RTW fares.

I am not aware of any consumer booking engine that ever allowed an RTW to be booked at the RTW fare.