I can't help with GPS co-ords for Rat-a-Tat, but I remembered that I had a hand drawn map from my BBW days in the 1970's that we used to photocopy and take with us as there was always some confusion about finding the place in the rainforest. There used to be many false leads from folk bashing around looking for the hut, so these directions were shared amongst the club members. It's a piece of history now, and may not be of use, but then again the hut hasn't changed location in all these years. I can't recall with any confidence who did the original sketch, possibly Ted Wassenberg or Lance Rutherford, but Ron Farmer from BBW might know if shown a copy. Anyway, let me know if it was of any use