Anyone here ever taken an optically junked lens from an RB 67 and mounted a new lens in the shell? I'm specifically thinking about getting a junker 90 or 127 lens and putting some kind of Petzval or meniscus lens in it so I can get those cool portrait effects but still have the focus and exposure control, and not have some totally klugey lens mount that I'm worried about it falling off the camera every time.