SICF namespace node

[sapmanie]

Hi,
Am creating a custom service in SICF. When I go to create the service under default_host, I get the message: "If an SAP partner or customer has acquired a namespace from SAP, it is recommended that..this is created as a top node".
Well the company doesn't have a namespace but I would like to have new services created under a custom node - I'm thinking it is similar to create a Z development package for customer ABAP, so all new custom services would be in the one place.
How is this done as I can't see a way of creating a top node? Or can I just go ahead and create services under SAP delivered nodes, since every tutorial I've come across seem to add them all over the place - like sap\bc etc.?

Thks,
sapmanie