C2, I am posting the information up for you to use as you see fit as some small token of appreciation for all of the great scripts of yours.
Once I hit 66 skill the difficulty for my trap spots all dropped by one order of magnitude. I should have moved again, but I was working. It took moving three spots out to sea for the first move to put me in the easy/optimal/challenging skill range. I checked again for this move and it put the difficulty ranges back to easy/optimal/challenging again by moving three more out to sea.
I suspect for taining mode you could require a skill ball, have the use put land off to Port or Starboard (and tell the script), and have the script move the ship over three spots when when it needs to increase difficulty. It looks like the first two steps up are 59 and 66. I suppose you wouldn't need a skill ball, you could just set it to move at skill intervals, but the skill ball messages would be a nice way of doing it since the messages end up in your journal.
This may be a really great way to train fishing. I certainly would not have a couple of million gold in stuff I could sell at 66 fishing using a pole...