Hey Thorn Bird,
Na, I reckon I got it right.
With a retrieval out of Barrow we used to arrive in Perth with around 1200-1600lb of fuel depending on the winds southbound. Its not much when you throw in an hours holding and a couple of approaches. We would burn around 1600pph, from memory, at F250 for a TAS of around 370. Any higher and the TAS would drop off pretty quick. This was a C550 SII, so a little higher than the weights you quoted.