Definitely a tricky one. Some similar species have all black hindwings (e.g. Cryptophasa pultenae - males I think) others have part black hindwings but predominantly they are the inverse to this moth.
@ibaird @WendyEM @donhe I had a reply from Ian Mcmillan regarding this species; "Probably Cryptophasa chionodes, a sexually dimorphic species. Males are black and very much smaller. Graham Cocks found it in Townsville. Also known as Cryptophasa sp. ANIC74."