If we can come up with a supersonic vitesse whilst retaining the 25 foot turning circle I think we may be onto a winner, though I fear the standard fuel tank may offer inadequate range.  

Don't know John. I suspect a combination of reasons mostly practical. As would be the case with fitting them extensively on a Vitesse. 

Boundary layer splitters!   But why does a lorry have them on maybe only 10% of it's front edge?

Those lorry vent things look smart. Technically I suppose you could do them on all of you sharp corners. Both sides and the top of your bonnet. Trailing edges of the roof and boot. C pillars. Fair amount of work, but potentially useful!

Gosh, EE, apologies!   I should have put it 'I don't understand'. John

If by "supersonic" you mean REALLY noisy... I can confirm mine is from about 75mph upwards....  (By 100 mph it's REALLY REALLY noisy)

Like i said. It's the French. 

You've just said you don't know and then the slander my suggestion. Go on, prove I'm wrong!  No and you're welcome to that one. However... without such a model I would suggest that without changing the silhouette of the Vitesse completely your best approach would be to try and modify the airflow round all the corners to minimise turbulence on that slab like front end. That would mean fitting boundary layer splitters on the verticals at the bonnet and windscreen pillars. Basically like those 'wings' you sometimes see on the front corners of lorries. Get the air moving smothly round these and it will tend to straighten out and draw off the turbulent air trapped across the front and round to the side of the car. And following on from the Vitesse estate rear radiators if you can duct as much hot air from the front of the car into that dead air space behind it that will also reduce drag. At higher speed/hotter temps you may even get a little extra push. It's what F1 does these days. If you could get the Vitesse supersonic you would even be able to use inlet pressure recovery to provide thrust. Concorde got something like 60% of it's thrust at Mach 2 due to the pressure recovery in the inlet duct to the engines where the air velocity was reduced to the subsonic speed necessary for a jet engine.

And now for something COMPLETELY different.     We're a few days after the Twelfth Day of Christmas, but still, 'tis the Season to be Jolly, and no one is more jolly, sometimes to excess, than Giles Brandreth.   For it was he who set up a fund raising evening last year in aid of the Orange Tree Theatre in Richmond. Surrey.   So far, so so, but he assembled a stellar cast of British actors, to talk about Shakespeare's Twelfth Night.   Actors in their anecdotage may not be your thing, but I think they are funny, and moving.  And, be prepared to be moved beyond measure, again, by Judi Dench! Clear the stage!