I have not used Sealux macro nor plan ports for macro on the FS7 setup. If you are shooting Macro ONLY, there is an advantage.
Thank you again for excellent explanation and recommendation.
You said before "Zenunderwater 200mm (8") dome all the times - no other ports were used even for close-up shots".
In spite of that, I thought that you have some experience with Macroport or Plan Port (produced by SeaLux) which is recommended for macro objective like Canon 100,
Agreed. I came across this interesting article that says dome ports can be used for both Wide & Macro. And since flat ports can only be specific to macro - not for wide angle shots, I prefer the dome for more versatility. This works well for the Sigma 17-70mm mentioned above.
what I read out of Thani's setup description is that he only used the Zen dome, not any macro specific port. And to be honest I only bother to take a macroport if I know I spend a larger number of dives during any given trip with muck.