Hi David - the main difference between your model and the one in the tutorial is that your bottom closed curve is not a smooth curve, it's made up of 4 segments and each segment connects to one another at a sharp point rather than a smooth connection.

Then when generating a network from that, you will inherit that sharp segmentation into the network surface as well, instead of getting a single simple network surface you will instead get 4 separate faces that are sharp to one another, that kind of segmentation will also make filleting more difficult as well.

Try getting the bottom shape to be smooth and it should then resemble the tutorial a lot more. You can do that by selecting the bottom curve and doing Edit > Show pts, then grab the corner points and use the Transform > Align tool to get the points lined up vertically and horizontally to the center ones, that will then make for a smooth bottom shape.

- Michael