I would hate to see him get away from that excellent acceleration up and across the ball. If he starts trying to flatten it out too much and get early racket speed, he will lose the up and across, as well as the excellent acceleration he currently exhibits. He appears too humble to argue in favor of how what he is doing is more correct.
I too hope he doesnt' mess with that swing - it's a very nice swing path and grip. I don't think a person really loses their swing technique even after long breaks.
One thing he could do to setup balanced more upright vs. balanced up and back, is NOT to take his left arm as far back with the racket. I had this very problem and it causes balance issues. As the racket is taken back even with the shoulder, that left arm should release, and go ahead and extend OUT to the side vs. going back further which causes the whole body to balance too far back. Unfortunately, this is not easy to fix, even though easy to diagnose.
MTM is Modern Tennis Method, developed by Oscar. It describes the way almost all of the pro strokes are executed. MTM is clearly not the only way to learn it as many players do it naturally till they get coached out of it, and many coaches are experts at teaching parts of it;
but what is quite special about MTM is the completeness of the system and lack of false data.
Yeah - I have recently seen some of this due to you guys on the forum. I have to admit, I have been working on this via this forum, John Yandell, and through personal analysis of pro strokes in slow mo. ie, I changed from classic to modern forehand with great results, and VERY MUCH easier timing in hitting shots, especially hard or heavy shots coming at me.
What feels odd, is that although I and other will give Oscar his dues, it seems like he may feel bitter than his information was not originally well recieved. And that's a bummer ok? I wish I would have heard it many years ago! But there is so much information about the modern forehand now that it just seems a quite strained to hear MTM touted as the greatest method. That's my personal take, and I take not one iota away from Oscar or his method. The way it is presented just seems as I said....'strained'.
However, with that said - using basically the same ideas, I am one of those guys who did make a transition, and have been competely blown away with new technique regarding the forehand. I saw some of teachingtennis' vids, and that is how I hit now. Same good stuff.
PS. Have you noticed with the SW and Western grips, and open stance, and big topspin, a tendency among many students to get away with hitting late or off the back foot? Even Andy Murray does this more than I like.