Hi propmaster, it sounds like you're all set up ok now thanks to Pilou?

re:
> What am I missing? Shouldn't Rebuild have removed the seam?

Rebuild in its "Refit" mode will only glue together segments that are tangent to each other. If there is a tangent break in your curve it will rebuild each of the smooth parts separately.

In "# Points" mode there is a "Keep corners" option which you can disable to have it ignore sharp corners.

So probably there is a little bit of a tangent break in your curves in the area where you're getting the unwanted edge. If you can post the .3dm model file with your curves in it I could take a look to confirm that.

- Michael