I am left eye dominant but right handed as well. When I first began shooting my dad taught me to shoot right handed because well thats how he did it, it never felt right but I could do it adequately. Once I came closer to hunting age my dad noticed I was struggling and suggested to try left hand shooting after some testing proved I was left eye strong. For me it was a world of difference everything just fit and I haven't looked back since.A number of years ago I went to my first left handed bolt action rifle and will never own anything but in a bolt. This change has made for a better fit personally which to me is extremely important for shooting.

I would personally wouldn't force him to shoot one way over the other, let him try it both ways till he can make up his own mind which feels and works best.