Contralateral tilt

My son has a significant contralateral tilt when he pitches. He is a true over the top pitcher. His head tends to move to the glove side and tilts (like he has water in his ear). Mechanically I realize this is far from ideal. His mechanics are pretty solid and he does not walk very many batters. I am not sure what to do. Any suggestions would be greatly appreciated. Do I leave him alone and let him continue or try to change his style. I think he is very stiff in the hips and I believe this contributes to the tilt.

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