Hi Lewis, so Flip in MoI will only work on an entire object, you can't flip just some faces inside of a joined object. That's why you aren't getting any changes when doing the Flip. In NURBS modeling the orientation of a face is automatically determined by its topological connection to neighboring faces. Then it's possible to flip the whole structure.

Thanks for sending the object - it looks like there are a couple areas that have slight overlaps instead of being cleanly joined, and maybe there are some degenerate faces there. A degenerate face is a face that is squished down such that it has no surface area, it can potentially mess up topological face traversal.

I'll examine your object more closely to see if I can tune it up and send it back to you.

To see the potential problem areas, set up a shortcut key for highlighting naked edges as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6051.2

- Michael