What powders do you have available to you? I have information for American Alliant/Hercules Blue Dot, French Vectan AO and British Nobel 82. Don't know what components are available to you in Australia. I will help if I can. Did you chase up that lead to the 8 bore loading book I sent you? Lagopus.....
Someone I know has a photocopy of the Douglas McDougall book; at the price, I won't be buying a legitimate copy!
ADI powders are the generally most available here; some are sold elsewhere as Hodgdon powders. At the moment I'm using BP, as mine's BP proofed, but some lower pressure smokeless loads might be good for case life.