Thank you both for your help! I feel a lens upgrade coming on from D to G.

Thanks Catherine, you may well be right! I will check!

Since starting to use the FB ring, I have been having trouble with poor/non-existent stacking. I am using a Nikon 800E with Nikkor 105mm f2.8D lens.When I first tried to progam the tube, I clicked on the wrong lens i.e. the Nikkor 105mm f2.8G so I assume that is why the result is failure in that no ...