You have the cable. You have the plugs. You aren't using the cable for any other purpose. It doesn't hurt anything; in fact it can only help by spreading the CPU power across more wires resulting in less voltage drop to the board, OCing or not.
Just plug the 2nd CPU cable in! I don't understand the resistance (pun intended) to plug in the 2nd cable.
I did on mine.
I think maybe you misunderstood what I said in my last post. I have 3 CPU cables in total for my HX1000 PSU. And yes I will be plugging all 3 in. I was just saying that the third cable on the Mobo side has only 4 receptor holes, so the third cable's 8 pin plug on the Mobo side will need to be split, with half used and half unused.
So in summary-
Cable 1- 24 PIN ATX from PSU to MOBO
Cable 2- 8pin from PSU side to 8 pin on Mobo side
Cable 3- 8 pin from PSU side to 4 pin on Mobo side (split on Mobo side as only has receptor for 4 pins).