Hi Danny,

> I believe a Nsided surface should be tangent to each mating surface in this case it's not.

As far as I can tell it seems to be tangent to each mating surface, a Zebra stripe analysis of the default generated patch looks like this:



Note there how all the zebra lines touch each other across the boundary lines? That means they are tangent.

I can see what you don't like about the patch though - but it's not that it's not tangent though it's that there's a kind of build up of curvature in a relatively small area near by the outer edges of the patch. Currently the n-sided patch mechanism has a tendency to do that kind of shaping, I do want to try to explore some different ways to reduce it.

Sometimes tweaking the "Bulge" factor can help.

- Michael