Hard question to answer definitively. Have you tried anything in particular?
9.5:1 compression ratio seems light for that type of setup. I could be wrong but relatively lower compression on an injected alcohol combo just seems like an odd situation.
Does the methanol make it run cooler? Might want to consider a hotter plug but again, I am really not sure on that.
In any event, can you get Autolite in Australia? #3924 seems to be a popular choice. I use them, no problems. Seemed to work as well as the Champion RC9YC that I replaced. I have a more conventional set up though; approximately 10.5:1 C.R., open chamber iron heads, carbureted on pump gas.