if I am thinking of the correct incident at gawler, it was a Onex, not a Sonex, it had significantly modified controls to suit a disability, there was a real question of the pitot placement giving erroneous readings of airspeed, Sonex do not recommend extended ground testing of the aerovee, the test pilot was not from Qantas, has flown regularly since, is a far better pilot than I will ever be, and has done at least one other test flight that I am aware of since.
I had a local aerobatic pilot test fly my plane, he had never flown a similar type before, flew it perfectly, greased a three point landing first time. My nerves were bad enough watching him, I am glad I didn’t do the first flight. It gave me great confidence for the subsequent testing.