I don't see why you'd want a 90mm f1 lens on a rangefinder, anyway. With that little depth of field, I want an SLR so I can see if I'm sharp or not. If you stop it down enough to be sure the rangefinder will have you sharp, you might as well get a cheaper lens.
It's a Leica. If the rangefinder says it's in focus, it's in focus.No need to stop down.