That was quite a task. Hardworking guy. Nice attitude and sense on humor, too
To refine things, he could use open tuning in order to avoid left hand pressure influence variations.
And he should device a constant force strummer - i.e. a free falling hinged mallet or something like that.
Finally - the whole contraption could be bolted on a jig to get rid of "hug-variation"
I'm sure he is aware of all these things - seems to be a smart guy - the kid , too . . .