Poteroo, you state: "I think you might find that in GA you can fly at low level around a private property, with owners permission - but with several conditions, one of which is completion of the LL course as per CAO 29.10"
You are correct, however in Ultralight a low level endorsement is not required; in fact it doesn't exist, so no conditions as such. It's one of the only differences between RA and GA.
PA39, if you see something you determine to be "illegal" the report it and it will be dealt with. I don't think your average pull-up is going to stress your airframe significantly. Aerobatics of any kind aren't permitted in RA-Aus, so again if you see anything that shouldn't be done, report it (02 6280 4700, Lee Ungerman - Operations Manager. Your efforts will help clean up the sport for everyone to enjoy and for you to enjoy when costs get too high or you aren't able to get your medical any more...
The word on the street with the Allegro is engine failure and or potential C of G issues. It was apparently kit built with a high-time used engine.
Any RA-Aus can be maintained by the owner with no qualification or experience, however hire-reward aircraft are maintained by Level 2's who are usually a mechanic of sort given the qualification from RA-Aus with a reference from another few L2's or LAME's. It's a moderately controlled system that works fairly well.