The setup I'd like to support would be a Canon 5D / 16-35mm f2.8L (version I). I'm considering purchasing a NN4, but can't find the relevant maximum Upper Rail Setting / URS / setting B - what is this length? The data on the website seems to be incomplete except for the NN3/NN5.
The max URS of NN4 with CP-2 is 139mm with the short end of the base plate of CP-2 to the end of the rail. The mark on the base plate is situated 2/3 to 1/3 of the length of it. You can mount it visa versa to the upper, thin CP-2 plate. URS max on NN5 is 149mm.
http://wiki.panotools.org/Entrance_Pupil_Database I have to use this database cause I am a Nikonian. The URS = Upper rails setting should be L1+L2 from Wiki database. As often, there is only one zoom setting for your lens mentioned: 16. L1: 38,5 for 5DMKII + L2: 79 for 16-35 @zoom 16 = 117.mm for your URS.
Normally zoom lenses tend to move backwards on the upper rail. Sometimes the next zoom setting from 18 to 20 needs 2mm backwards, but Nikkor 18-105 on D7000 for example needs 37mm from zoom@70 to zoom @105.
Sometimes it is even more extreme. Cause it is 16-35mm, I would think from my experience testing a lot of Nikon lenses, this can be ok on NN4. Sometimes, like Nikkor 18-200 VRII, you have to use the upper rail the other way round in case entrance pupil is situated behind the sensor of the camera.
In case you do not know the rest of your URS zoom settings, you might ask Andrew Badders, one of our 3 best NN EU distributors and resellers besides Vincen FR and Mauro IT, to change the NN4 into a NN5 or M1 if needed. Or visit him in Scotland in case you are nearby.