Ok all, Third post since getting into this....Here is my next question and I have looked and searched the forums.

I am trying to find the Nodal Point on a D3s and a 70-200 VR II lens with a NN5 and RD16. Using John's string method to find the bottom rail measurement, I have come up with a 88 to 87. Other have emailed me that a D3 should be 86. I am toooooo new to argue or understand to that is my post question. Is there a difference between 87 and 86?

Finding the upper rail measurement, Johns method of moving left and right +/- 30 degrees makes the lens itself block the visible nodal point viewable in the lens at 0 deg. Should I do it less than 30 degrees left and right? A little help with the longer lenses is I guess what I am asking for too.