Yes, typically talking to yourself or pre-recording yourself speaking is much easier than speaking to an audience. No threatening, judgmental eyes staring and evaluating your every block, repetition, and prolongation. I think you have a great idea, if he is in fact so shy/hard to understand during a presentation, having him pre-record the presentation is a good substitute. When I was in college I would print out my entire speech and read during my presentation. I was always much more fluent while reading out loud, so I incorporated this into my presentations.