I fished with Bobby Jones in 2002,
http://www.marlinaustralia.com.au/
Had pretty tough fishing for the week, but we managed 300#, 350#, 500#, 850#, and 900+# Black Marlin in a week of fishing. If you can imagine this, we used 8-10# Skipjack as live bait, on 120# test spectra with mono topshots. It was a true experience.
When we fished dead and skipbaits, they were this size.

Bob travels south (toward NSW) when he is not in the summer prime billfishing season (Oct-Jan) and hunts smaller billfish down there.
Getting there wasn't easy, but it was fun!