None.And it is not a theory, it is only a hypothesis ( it is a "let us suppose that..." statement).To be turned into a theory, it needs all kinds of other, weird hypotheses, such as a "metric" (rule to measure distances) that is very counter-intuitive.And of course, it would require drastic changes in the understanding of all kinds of other phenomena (for example, since the hollow Earth has no core, explaining Earth's magnetism gets very complicated).The biggest hurdle might be gravity. To explain gravity in a hollow Earth requires such a different mechanism that the Moon could not have any gravity (or, even worst, would have "negative gravity"). Or, since we know there is gravity on the Moon, then we have to conclude that the Moon is also hollow and that the whole universe is inside the Moon.But since we started with the hypothesis that Earth is hollow and the whole universe is inside Earth, then it cannot be inside the Moon.A sort of proof by contradiction against the idea of hollow Earth.