SixMaps says the property is 16038 Hume Highway Marulan. If you Google
that you will find a
Mr John Dugan resides there and has
a Mustang II registered to that address (FWP).
I couldn't track down a phone number, but that's a starting point.
EDIT: And if that isn't a reason to hide the details from the public on the CASA register, I dunno what is. From such a simple question you now know who lives there, his families names courtesy of
this document and the fact that he is 'rich enough' to own not one but two airplanes courtesy of
CASA's own website