One's position in space-time is an inextricable component of "the self". Even in theory, a perfectly replicated individual has already fundamentally diverged from the original just by virtue of its existence as a duplicate (since duplication implies a distinct position in space-time). Ultimately, what I'm saying is that the idea of a "perfect duplicate" is something of a contradiction, and any theory of mind that attempts to define one's "homunculus" in terms of a physical brain state is in some ways moot because although our human senses might indicate that we are dealing with two identical individuals we are actually dealing with two fundamentally distinct beings, despite the apparent similarities.