Steve,
I was lucky enough to get a run out in the 3 wheeler at Silverstone some months back ( although I wasn't driving
) the sorts of speeds you are talking about are certainly not beyond the limits of the 3 wheeler. In terms of distance highway driving that will be a lot more difficult to judge and my guess is that with the wind in your face the driver will be suffering long before the car is.
As winters starting to settle in over here it might be a few months before anyone can report back on any long distance runs
