I have been using F-1 cameras for about twenty years. When I ran out of mercury batteries, I went to the CHRIS MR-9, and my meters stayed accurate, across the scale.
Later I had Ken Oikawa, former Canon technician and F-1 specialist, tune up an F-1n body. He converted the camera to use a 1.5 volt 625 battery. This is the standard conversion that Canon recommended. But this left the meter accurate only in the middle of the scale. It called for underexposure in high light values, and overexposed in low light values. Ken then studied an MR-9 converter with the camera, adjusted the meter for that, and concluded that in fact the meter was indeed more accurate across the scale with the MR-9 adapter.
So I have concluded that for me it is totally worth the price of an MR-9 adapter to provide an accurate, dependable meter on such a fine camera.