Paul Kay, Thanks for the post. I'm well aware of the technical theory of the zoom lens and finding the "best" solution you mention. I guess my solution is to get the test charts out along with the various Seacam pvl extention rings and lens and do some tests until I happy. I also have an assortment of fixed focal length primes I may resort to for a project later in the year.
I'm interested in what results you have been getting since you posted this last Dec, Seacam recommends 60 PVL,checking the Seacam home site they recommend the 70m PVL? I recently upgrades to a Seacam full frame(Nikon D3/D3X) and have both the 14-24mm and the 16-35mm and am trying to decide which to use. Also recently introduced is the Nikon 18-35mm which looks interesting.
While Wetpixel was taking a nap,I emailed Steve Frink my tongue in cheek solution to the 12 exposure limit, he posted it on his facebook page, it appeared om July 1, also check Eric Cheng facebook page he picked up on Steve Frink's post, he posted on July 2, you will also see some interesting comments.
re: 12 exposure, in 1965 Kodak came out with 220 roll film,which worked in most cameras using 120 roll film, the problem was not all films were available,I don't know if and what would be available now days. There was a trick to using the 220 roll film in the Rollimarin,,once loaded the film advance is registered after that you could advance the film carefully and with practice and get 23-24 images per roll. processing 220 film was another challange if you haven't tried it.
It took the skill of a Nikkor reel Ninja to load the 220 film on the stainless steel Nikkor reels.