Thanks for the quick response! Much appreciated.
I just want to clarify what you said about "two short trips being a problem is not a valid concern". My understanding was that a one-off activation trip (short trip on a return ticket) is not a problem in most cases, as long as you then make the "permanent" move within 12 months or so. I had thought that the permanent move had to be the next trip after the activation? Is that not the case?? (I hope not - it would make it much more straightforward for me!)
So hypothetically, if I head over to activate in June, that obviously won't be a problem. But then, my worry is that when I next lob up at LAX in September for a another short stay before heading back "home" to Australia, they'll see that I haven't made the US my permanent residence yet, and deny entry. Because I wouldn't have substantial ties. Are you suggesting that they might actually be a bit more lenient? (Again, I really hope so!).
Thanks again for your help.