Consequentially, only zoom lenses that don't change its physical size significantly while zooming are suitable for photography with a dome port. Among the Nikon FX lenses, the 16-35mm f/4 is much more suitable than the "legendary" 14-24mm f/2.8, the latter changing the position of its front optical element strongly while zooming.
Not entirely correct. I have here the Nikon 16-35 f4 and it changes the position of the from element, getting 9mm shorter when going from 16mm to 24mm. From 24 mm to 35 mm it moves out the front element for about 6mm. So there should be other things to consider and not just if it changes or not the front position element while zooming. It also moves a lot (around 30 to 40 mm) the position of the rear element while zooming in from 16 to 35 mm (maybe this compensates?).
In terms of the 16-35mm with Nauticam and 230mm dome, the correct extension seems to be between 60mm and 70mm, with most people opting for the latter.
Nauticam recomends a 90 mm extension. Do you have any comparation test shots where you've based your decision about the extension length?
I use an 80mm extension, just because that's what I have here (although image quality is very good, with the normal limitations of FOF and dome ports - using a big 230cm).