Hi, I am also considering doing shadowing on a visitor visa. I am a female dentist. I already have a B-1/Visitor visa. But when I read closely on Immihelp forum, it says that dental observation/training is not allowed, only medical training is permitted. The forum says that when I get to the US airport, and the customs officer asks for the reason befre he/she gives out the I94, saying the you are going for dental shadowing may not work. So I am curious as to how you are thinking of doing it on visitor visa...