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I've been using a Russian bow hold ever since I saw this video by Christiaan Van Hemert and it's been really great to play this way. A lot more comfortable and just feels right to me.
Now I've taken this a step further and started to study old film of Heifetz playing. He uses a similar grip. But from what I can tell, Christiaan bends his thumb and angles his fingers more than Heifetz, whereas Heifetz seems to have a straight thumb. I guess I have to keep experimenting to see what works the best for me, but I thought it might spark some interesting discussion on here. Although I could be wrong, since not a lot of people use this bow hold.
I think it's great and maybe somebody else out there will try it and find that it works for them too. Although be careful if you have a teacher who doesn't approve.
Here are some pictures I was able to get from the Heifetz films and from Christiaan's video: