Has Paul come across the Alexander Technique? This does wonders for managing bow speed and other variables whilst maintaining good poise such that shoulder height and spine length and shape are supported. I started learning age seventeen and now in my sixties.

Hi, when I play pieces like Vivaldi sonata in a minor and there is a lot of fast shifting, my left hand hurts; especially down my thumb and into my forearm. Do you have any suggestions?

Hmm. Why can't we shift the sound point, just like Fischer teaches? Why can't we vary the "weight", by shifting the emphasis we put on our upper body through the bow arm? Nice video, but ... Hmm.