It looks like what you want is not to have separate port elements, but to treat the whole node as a single port. That’s actually the default behavior. What some of the samples do, such as FlowChart and LogicCircuit, is provide several ports per node because they have logical and physical connection points – it matters exactly where a link connects.
But I suspect you don’t care exactly where a link connects to a node – they are all logically the same, and the actual points may change so that the diagram is easier to understand. This can be achieved by setting the go:Node.FromSpot and ToSpot properties to “AllSides” (or if you need, some subset of the sides). Some of the samples demonstrate this, such as EntityRelationship (ER Diagram) and the tanks in the Piping sample.
The LinkDemo sample lets you explicitly control those properties for selected nodes and links. I think it starts off with various nodes in different configurations.
Did you start with the FlowChart sample? If so I suggest you greatly simplify the Node DataTemplate(s) to remove all support for separate ports. In fact, it might be easier to just create new Node templates, copying only what you need, because you can also simplify the code-behind a lot too.