I will be interested to see if it fits on Subal ports. The largest lens I have is the Nikon 17-55, and with its filter thread of 77mm it fits tightly in the fisheye port but doesn't fit through the extension rings. This new 16-35 lens has an 82mm filter thread.
I had the same thought this morning and did some rough measurements for Seacam ports. My 17-40 lens barrel protrudes a little beyond the 77mm filter, about 80mm as I eyeball it. The new lens will be another 5mm or so wider, so figure 85-87mm diameter for minimum port orifice.
Also, make sure there is enough room for a zoom gear, and ideally a focus gear as well. I'm going to want both zoom and focus on this lens.
The Seacam looks like it can handle up to about 95mm in diameter, so I don't anticipate an issue there. The lens is 111.6mm long, btw, so it will no doubt require a different port extension than existing 16-35/17-40. Lens specs below:
