I own a Pilates studio and have seen several clients who also see one of my other instructors. I actually like it a lot. Everyone has a slightly different style and sometimes the way my other instructors do things resonate better with the clients than what I do and vice versa. It’s also nice to have more than one set of eyes on a body to figure out what will best meet their needs. That said if I wouldn’t feel comfortable with them training my clients I would never have hired them so I have a high level of control. In the past I have taught a class once where I taught the tues night class and another instructor who was terribly unqualified taught the same class on Thurs. night and it was a disaster for me. So how about a qualified yes if the other trainer is compatible with you and your style. I also have some clients who do Pilates with me and see a traditional personal trainer and that has worked well as well.