I beleive the english definition of 'trim' referrs in one way or another to a particular area of a lady. The definition meant was about a decorative piece of wood of one sort or another that would cover the blemish, either by making the edge piece of wood longer / lower, or by replacing the veneer on the plywood.
After giving it some thought, I suggest you try to combine the two and after you stop the rot from progressing, get a decorative lady to hang around your boat using her 'trim' anyway necessary to make sure you don't see the bad spot on the boat....
