'Might end up with serious neck problems.' (from the first post)

I looked at the video. I think that rather than causing neck problems, his posture makes it easier on his neck.

Just yesterday I talked with a woman aged 84 who was bragging about her ability to parallel park in a tight space. She mentioned that many old people cannot turn their necks to the side (arthritis in the spine, maybe) and so have difficulty parallel parking. The fiddler in the video is probably cannot turn his head much to the side. Since he cannot turn his head to the left to hold the fiddle in place, he has moved the fiddle forward.

Moving the fiddle towards the center of the body also seems to make it easier on the right shoulder, which moves the bow.   

He should pay attention and make sure that nothing new is starting to hurt because of the new position. As a nurse I once new said, "If it hurts, quit!"

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When I had my piano tuned, the tuner mentioned that at every convention there is a presentation on who suffers more hearing damage, piano tuners or violinists. The violinists seem to be the unfortunate winners of the 'contest.'

Moving the fiddle towards the center of the body also makes it easier on the right shoulder, which moves the bow.