Tony,
That bloody 577 of yours would be close to the ultimate in thick scrub pig stoppers I would think, and a damn fine bull killer as well.
One day I might have a go at putting one together myself.
Another good cartridge as you are well aware is the old 500 bp shooting the nitro for black 440 Woodleigh loads.
Our mutual friend PP has certainly taken a lot of good territory boars with his!
Yes we are indeed fortunate to have plenty of game in Aus and plenty of country well suited to double rifle hunting and of course a good number of keen double rifle hunters.

It's true that the "large bores" work really well on "large boars".
Shooting on open grain stubble my little scoped double in 7x65R works great as shots are often taken at 150 yards or more but that is not the rifle for NT jungle hunting.
For that you are best off with a large bore heavy bullet moderate velocity open sighted well fitting double.
Ah yes, pure heaven!