Hi David - another thing I noticed in this model is that this surface here seems a bit odd:




If you use Edit > Separate to break it apart from the other one and then turn on its control points, you can see that its control point grid is kind of badly formed and kind of squashed together:




It looks like this was created as something like a network surface between 3 curves like this:




Usually it's better to construct something with a rounded outline like that by first making a simple broad rectangular surface (which will then have a nicely formed control point grid and not be squashed together anywhere) and then trim that surface by a side profile that has the rounded corners in it, more like this:










A surface created in that way by a more regular initial rectangular base surface, will retain that surface as the underlying thing below the trimmed away areas:




Just in general you will tend to get much higher quality surfaces with this method - the other way you can easily get ripples and bumps and even self-intersecting areas by trying to build a network directly to a non-rectangular outline like the other one.

- Michael