Direct CU II 7950 comes with 2 6pin connectors, but if you look where the pcb is soldered you can see 8 solder points below the right 6pin connector. Would it be difficult to put on an 8 pin? More importantly could it increase OC ability?
The 6-Pin is officially 75W but actually can provide more than that. The additional 2 pins in the 8-pin are basically ground from PSU. The idea is not to overload the 6 cables in 6-pin with the additional 2-pin.
I don't think you should do anything to it. It would not increase overclockability and it doesn't depend on 6-pin or 8-pin power connector. But the VRM power phase and the chip itself.
The 7950 will draw power from 2x 6-Pin PCIe power directly from PSU and from the motherboard PCIe slot.