The SRR650 is not made in the old Avon factory, but in the main Milpro facility in Spain.
You are correct on the twin engine limitations, I think they've erred on the side of caution with these.
If you need any more info, you can email me on firstname.lastname@example.org
We are in fairly regular contact with the Milpro guys here and they're very helpful although answers can be a bit slow coming from the factory.
We are a dealer for their boats as well so would be happy to quote and can ship to Oz no problem.
Chas Newens Marine