http://www.modernvespa.com/forum/topic5587.html,
I took my existing camera mount, previously designed for attachment to a cage headrest, and added two more holes to make it look like this:

On the left end, I have a screw that will hold my ballhead, onto which I will attach the camera via quick release. Pictures of that setup to follow.
The right end has the two U-bolts that hold the mount against the cargo rack like this:

and so:

(notice that the ballhead mount screw is not in proper position yet).
Mounted this way, the base is rock solid and can easily hold my DSLR with ballhead. I will secure both, in case they come loose by vibration, in which case they will just dangle on their safety line without hitting the scooter.
I think I will prefer a left-side mount, as this will show more road than a right-side position. In any event, the mount can easily be mounted on the right, it will fit equally well.
Exposures will be made by remote control and I will experiment with focal lengths to get the best views.
Who has done something similar with a DSLR, and what are their recommendations for lenses, exposure modes, etc.?