Apologies for the late reply Kent.
My son and I designed and 3D Printed this Adaptor for my Nikon 70-200mm lens. It locks in place just like the standard Nikon HB-29 Hood does. The two long arms sit through the fence, on the outside of two adjacent vertical fence wires, with just a little bit of movement either way. This positions the centre focus of the lens right in the middle of the horizontal and vertical fence wires (Camera in Centre Focus mode). Because of the length of the two arms, I can pan the camera right and left, and still maintain the centre focus position. The other advantage is that my left hand is free to adjust the zoom (handy when an aircraft is moving quickly), as I know the adaptor will keep the lens correctly positioned.
The other factors at come into play here are, the Zoom setting, and the Aperture setting (the zoom setting might act differently for other lenses). Shooting at F2.8 pretty much removes the fence wires, however I sometimes have to adjust the zoom level slightly if they start to appear. The down side of F2.8 is that the Depth of Field is very short, so it is better to shoot the aircraft in profile, rather than looking along the aircraft. If I have to shoot along the aircraft as it comes towards me, I adjust the focus position to be where I want it, rather that just in the centre of the frame.
After using the first Adaptor version for some time, we 3D Printed an improved second version (seen here) with the longer arms, and the locking mechanism the same as the Nikon HB-29 Hood. We printed the arms with a cylindrical hole the full depth, so we could slide in a metal rod to provide greater strength. The first Adaptor we 3D Printed in a rubber like material which had plenty of give, however we used a more "Lego" like material to print the second Adaptor (and I think it is better).
I use this almost every day and would be lost without it.
Note: To design the Adaptor correctly, I took a Micrometer down to the Security Fence to measure the horizontal and vertical spacing. I thought there would be a very standard gap in either direction, however, to my surprise, it can vary considerably.
