> I suppose I am assuming that the event horizon is always large enough to conceal a sufficiently massive object of extreme or arbitrary density No, it isn't.

> I suppose I am assuming that the event horizon is always large enough to conceal a sufficiently massive object of extreme or arbitrary density No, it isn't. It is impossible for a stable compact object made of ordinary matter that is smaller than the event horizon size for its mass to exist. In fact it is impossible for a stable compact object made of ordinary matter that is smaller than 9/8 of its event horizon size to exist. This result is known as Buchdahl's Theorem.