wrote in message news
Does this seem a reasonable/safe approach? It doesn't have to conform
to any specific wiring regulations (which it almost certainly won't),
no one is ever going to inspect the wiring of the boat at that sort of
level of detail. On the other hand I do want it to be safe for the
usual mix of family and friends as well as for me.

What does the team think?

A lot of fourway strips have integral fuses.
If you use one of these then the MCB will only be protecting the flex.
The integral fuse is providing the protection that the manufacturer thinks
it needs.
Of course, as you say, the 16A MCB will probably offer better protection
than the fuse anyway.