I'm technically ambidexterous, but my left had does most of the small, precise things and my right hand does larger motions and those requiring strength.

I play fiddle right handed. More precision is required of the left hand - it's finger-work. The right just has to learn how to operate the bow - the bigger motions of hand/arm work.

Maybe if you were to hand the fiddle and the bow to the pupil and tell him to pretend he was playing. He might very likely pick it up with the neck in his left hand and the bow in the right.