The great thing about anyone who's working in their trade more than five years that you can actually ask them "what were the most interesting projects you worke

The great thing about anyone who's working in their trade more than five years that you can actually ask them "what were the most interesting projects you worked on" and get a meaningful response. I would ask him about the experiences of what you just listed here and go with the flow. Also you may want to read about CAR (context action result) interview method to have a better understanding how should you structure your questions about these topics. What was the worst problem erformance wise he had to overcome? What was the largest team he ever supervised, why did he get in that position? If you talk about these kind of questions for a good hour or two you already will feel something about this person. You then have to transorm this feeling to a yes or no as a team. As he will be your future mentor and technical leader I would interpret the "yes,but..." And "no, but..." Answers as "no".