I had a guy fly with me once prior to my GFTs. He let me take a fundamental c*ck up at planning stage all the way around a nav ex for a form 170 check, intending to fail me from the word go. Instead though by going for a long flight as well he took a lot of money off me. At least CAAFU would have chopped me at a very early point. lesson learnt, fingers burnt.
Best of luck.