A "student" came to me to convert his PPLH to CPLH. He already had 20,000 hrs 747, owned his own H500, had a PPLH and 700 chopper hours. But the H500 was in a different country (same place he did his flying) so he had to learn in a Robbie.
He was tragic - couldn't cope with the skittish machine compared to the H500. Eventually we made it to the nav phase, and here he fell completely on his @ss. He could not fly with one hand, read a map, make a decision and make a radio call at the same time. He was so used to telling somebody else to do it and then watching them do it, that his basic skills were gone.
At my suggestion that he remain a private pilot and forget his commercial aspirations, he gave up, sold his H500, and went back to being a casual 747 driver - and soon after landed one wheels-up!!!
Time to retire...