VisualStudio.Net 2003 has a config file saying that it's for V1.1 CLR. If you write your own V1.1 debugger, you should do that too.
One big motivation is to ensure your V1.1 debugger creates the V1.1 implementation of ICorDebug. In V1.1, ICorDebug was a COM-object (we changed this in v2). In the absence of a config file, trying to co-creating an ICD may get confused if the V2 CLR on the box.