Thanks for the replies.
From talking to a few of the older players, it seems the Asst Coach who runs the lifting class has a pretty good track record. It seems he has pitchers on a different program. This is a class comprised of only baseball players, so it shouldn’t be geared to entirely mass muscle gain.
I do like the approach of finding a good trainer to teach him form before he gets there in the fall.
As to the Jaeger concern. I meant that he’s started their specific band workout, not the entire long toss program. He does long toss regularly, but it’s closely watched for form.