Middle is about right.
Stick him in a powerful car - he will need a large advantage coz he sucks
At the start tell him to slow down to keep him from getting too worked up
Keep telling him to slow down. The horsepower advantage should let him pass if he gets good drive onto a straight.
You can allow him to get a bit hotter when right up someones ass. It should get them worked up a bit too and they may make a mistake.
He will brake in annoying places, and the AI will out brake him into some of the corners. Get used to it

Once at the front tell him to speed up, or else his lap times will tumble. I used a Murcielago against things like Civic Rs and hot hatches. When B-spec was out in front, with no input he only managed the same lap times as the Civic, despite 4 wheel drive and 700 BHP.