D5 save AF fine tune with two similar lenses
I have a D5 and a 300/2.8D lens. Great lens, optics are superb. I bought the Kenko 1.4x 7 element tele converter to use as needed with this lens. The Kenko has the screw drive to connect the autofocus on the 300/2.8D, and I know from owning the Kenko previously that the optics are decent.
The lens alone requires no AF fine tune. With the Kenko, it requires -10. Thats not surprising, every other TC that I've ever tested requires a different AF fine tune than the base lens.
My problem is how to store the settings in the camera. When I use a later style Nikon lens with a TC-14E or TC-20E, the camera sees the combination of the two and saves the AF fine tune value separately from the bare lens. Unfortunately when I mount the 300/2.8D with or without the Kenko, the AF fine tune shows recognizes only the base lens. The AF fine tune window says 300/2.8 either way.
I don't see how to override the system to save two different AF fine tune values, for what the camera thinks is the same lens. I don't want to rely on myself remembering to change the fine tune value every time I mount the lens. Anyone know how to do this?