The wider lenses like the 28 and 21 u need to be careful w/ due to how close the rear element comes to the sensor or anything inside the camera body in front of the sensor. I don't remember if there is an issue w/ the 35, but the 45 and 90 u mentioned should be ok.. Just remember that your normal weird contax lens mount and unmount applies here as well..
If u are worried about it... The first time w/ any lense no matter if it is a contax or Leica... Put the lens on the adapter first to c if the rear element will be an issue before u mount to the camera body.
With the contax g mount, it is alway easier to unmounted the lens from the adapter before u remove the adapter from the body.
I don't have a contax g to m43 mount.. I remember reading about the big ring style adapter works fine for all the m43 cameras except the omd. The release latch hits the bottom of the fake prism area of the omd (where it juts out a bit under the lens mount area) during the mount sequence.
Gary
