How would you stop investors in your two public funds (and their accountants) from asking pointed questions about disbursements from one fund to the others? Do you plan to fool them for this amount of time, or bring them into the conspiracy?
And how will you sustain the conspiracy when your other two funds trail the market index by a lower combined differential than your other, internal fund is beating the index? Will you initiate a Ponzi, or something else?
There is a more realistic angle to attribute RenTech's returns to fraud. I don't personally believe it as I have friends there, but I believe it would technically work:
A nontrivial number of RenTech's employees have come from the intelligence apparatus of the United States; namely the NSA. Simons was particularly affiliated with them early on in his math career. It strikes me as plausible (but again, highly unlikely) that if RenTech is is a conspiracy, it is a conspiracy sponsored by US intelligence. They would have the capability to run a 30 year secretive conspiracy, and they would have they desire to attract top talent in math, physics and computer science.
But I'm just speculating for fun year. I really don't think there's any conspiracy :)