I been testing 16-35mm f4 topside with f2.8 II. New f4 is sharper corner and have better lens coating (better sunball).
I couldn't try it behind dome but still if I don't have f2.8 then I would buy f4. IMHO, both lens will give you better sharpness and contrast then 17-40.
Here is a before/after for you Bob, before is just raw and after is with neat video and a little color/contrast. Also sharpening in neat video is much better than unsharp mask (at least with the downscale in play).
With the compression I'm not sure if you can really see the noise the same way it shows on the source.
I noticed the nauticam port chart was updated recently, showing a 180mm glass port and adaptor with focus knob as compatible with the 7-14mm lumix. @escape is there an improvement in the corners with the larger dome? I would love to be able to run the lens at least at f5.6 and 7mm
I don't have direct comparable image from both dome but I can say 180mm dome is pretty good with wide aperture at 7mm.