A very good thread indeed.
I never knew Mark Hanna but like us all, could not help but admire is flying skills.
A sad loss to aviation.
On the subject of wake vortices I am reminded of an accident in NZ in the early '70's.
Mid morning, an agricultural pilot was returning to his base strip. The owner had decided to graze some young cattle on the airstrip, consequently they took some "shifting" by flying over and to one side to clear an area to land. The weather was perfect, frosty and still air (light drift). After 2 - 3 of these runs, just before commencing a "pull up" for a turn, the A/C inexplicably rolled violently though some 70° and the wing tip struck a woolshed, with fatal consequences. The A/C would have been at relatively high speed at the time (i.e. good control response.) The pilot was also very experienced.
The only rational explanation was lurking wake vortices, from previous runs.