I have had a lot of sports cars and test driven a good number as well. A lot of owners are like you and some wouldn't even let me drive the car, I had to sit in the passengers seat while they did everything. I could ask to do certain things like if they would brake check or accelerate, but that was the limit.

What I would propose is letting people ride with a trust local mechanic with the mechanic driving. That way they can make sure a professional is driving the car, can pick up on any issues, and can be honest with the potential buyer.