Regarding the question about the anchor, there are at least 3 Super Maramu Bow rollers. I think that you should make a cardboard cutout of the anchor you want and see if it will fit. It may fit on your SM, but not fit on others.
There are two things that you should look at, and these two things will likely answer all of your chain questions.
And download this file
which is "Anchor Chain, Galvanized dimensions and calibration.pdf" Clicking on the following will automatically download the file:
I have seen 10mm chain measure 9mm+/- because the zinc
is totally gone. Once the metal starts rusting I am sure that 10mm will get close to 8mm in some places.
I am sure that most of you know that a few months ago a Super Maramu was lost at a Pacific Atoll when his chain broke. It went on a reef and was a total loss. I do not know if the chain was defective, old, or possibly was cut by sharp coral. New chain is not that expensive when you consider what it does for you.