Wiley, I think that you are right. The fact that the US have ordered 4 "test aircraft" would indicate that they have specified their own fit instead of buying what other countries have ordered. The last article that I posted indicates the same boom being offered for the US aircraft - probably will have US made Probe & Drogue systems instead of the FR made systems. There should at least be airframe/engine compatability between RAAF/USAF tankers.