Hi Michael,

I was able to duplicate your tutorial just fine. See below for the 'oil slick' lighting which shows a very tiny cut in surface continuity. I created a path from the patch boundaries, and swept a small circle around it, then trimmed the resulting pipe to a shape which could then be used to trim a hole in the surface. Once done, I tried using BLEND, and while it worked, it created 'bow-tie' loops at the corners which left tiny holes in the corners. Other than the holes, the surface continuity worked much better.

Can you take a look at this file and see if you can trim out a blend area which stitches correctly? And if you're successful, would you please share your technique? Once I get this, I'll document in a video. Thanks.

File:
http://dl.dropboxusercontent.com/u/3788438/3D/TestRidge.3dm

Current file image. Note 1 and 2 showing surface continuity issue.