[750hp]

FWIW, Talking to a guy today with a 4 post hoist. He said the hoist manufacturer recommended 1000x1000 footings, 500 deep. He made it a neat cube and went 1000x1000x1000.

Having said that, he laid 590 square metres of concrete for the driveway and sheds, so what's another 4 cubic metres between friends...