Hi,
NSW State Archives have two files but from the 1890s, and one of those files is the deceased estate, locality Tumbarumba - long way from Summer Hill Creek both in decades and distance... BUT the files are for a chap surnamed KINSTLER ... perhaps that's the elusive name. If the 'farm' was named after the property owner, then we need to remember that 'foreigners' needed to become naturalised British Subjects to obtain title to land. So perhaps a search through the NSW State Archives index of naturalisations etc may turn up some possibles too.
Anyway, I used their keyname search option and entered KINS% (% as a wild card) to spot KINSTLER. There's lots of other surnames there starting with KINS, and of course you can use the % and then add letters after it too.
JM