I think I'm missing something. I don't see the target DC to navigate. In the example, it says 18, but in tile 5 (the only other place I saw that listed one) it says 15 and it's unclear if the GM how to make this determination. Also it feels weird that the smarter you are, the more likely you are to wrap over. Seems like that's counter-intuitive to the purpose. DCs are all over the place as well with very few using the standard DCs. It makes it harder to determine what I should be doing with the navigation since there's not a consistent target number.
Viewing post in Lost in Mortsafe Mire jam comments
There's no static Navigation DC as that would vary by environment and conditions (rain, dark, fatigue, rapids, etc.)
Just like the power meter, there's a risk of hitting the ball too hard — a high STR doesn't make you good golfer.
A high INT could be overthinking, analysis paralysis, overconfidence, etc.
You should reference the rules you are using when you change them. Especially when there are 2 sets of overland travel rules. One in the core book & one in the new material from the Western Reaches. The navigation rules do not set a DC which is why they are being expanded upon in Western Reaches, because it's unclear how it works in the core book. It doesn't account for the weather, familiarity, nothing. The DC check for it would be based on the standard 9, 12, 15, 18, 20. These checks are based on a natural 1d20 roll. You modified the roll, but not the DC after describing it as an "inscrutable labyrinth" that "proves... difficult." The question I'm raising is how difficult is it? Is it Easy on a sunny day? Is it Hard? How does the rain affect it? Does this change with the new rules? A little clarity would go a long way to making it more usable. If there had been standard DCs elsewhere, it would have been easier to determine what you think the environment difficulty for your adventure was.