You're very welcome. Someone, somewhere came up with the names of the trainees to put them in stone at the memorial. I would think they have a complete list, at least of those they have stones for. Did you ask if they had a listing when you contacted them?
Don't just focus on pilots as there were other officers that went through other training as well. Since you do have a fairly narrow window of when he left, you can narrow your search even further, potentially increasing your opportunity for success. Do you have any specific time frame as to when he left?