I have, in fact. The math that is used is very sound, and there is substantial observational data that supports it. There are a couple problems, though. Some of that observational data could also support something very different. Also, though many of the mathematical equations that are used are fairly easy to understand (if you are like me and enjoy Intragal Calculus), BUT they make some suppositions that are not necessarily well founded or solid. Think of it this way; one reason that the theory of relativity is still just a theory, is because there are a few obvious flaws. For instance, the speed of light is not a constant; it depends on what the light is moving through, etc. Still, the theory works and does explain many things that we see. Now, suppose someone comes up with a mathematical model based mostly on relativity, and another person builds another model that is based on that one, etc. This means that every subsequent theory is based on a theory that as currently stated, contains flaws, so every one of them has inherent flaws.