Hipsy is apparently the popular nickname of the time for Hepzibah. This census shows Sylvester as a Rhode Island native and "Hipsy" as a Vermont native. His family was from Westerly, R.I., where they were part of an early Sabbatarian community. Hepzibah Barton Satterlee's family had roots in Massachussetts, going back to Salem on the Barton side. At least one ancestor was under suspicion during the witch trials.
I believe Sylvester's father Jonathan Satterlee was also in the Rev. War. and may have also been at Saratoga. I've seen it claimed that he was at Bennington, but haven't seen the documentation to back it up.
And.... On you comment about Dutch ancestry (Perrin readers -- this isn't relevant to you), I have a funny story. My father's family has always said they had heard they had Dutch ancestry, but they thought it was on their mother's side. Until several cousins turned up the VanZant connection a few years ago, they were unaware of the Dutch roots on the father's side. However, in researching my grandmother's family, I haven't found a single family that was Dutch. She had ancestors from England, Scotland, Wales, Germany and Switzerland, but none that I could find from Holland. The answer wasn't all that elusive. They weren't Dutch, they were Deutsche! The two terms not only sound alike, but were used more interchangibly in earlier times by English-speakers who didn't necessarily see a distinction except in dialects.