What would you (or your Si-fu) say if one of your students trained with someone from another branch of the Wing Chun family, or from another system altogether? Would your reaction be, "Interesting! What did you learn?", would it be, "Look, what you do privately is your own business, but keep it to yourself and don't go blabbing about it in our kwoon", or would it be, "If you want to train with somebody else, you are not welcome around here. Now get the heck out!". In short, how accepting is your school of cross-training, especially when it comes to your closest "competition"?