I made some experiments today, but G 2, TC 8192, I 13 is the best setting. Unlike scrypt, overclocking engine can increase hash speed much more.
It seems those are the best settings for me, as well. Although I changed G 2 to G 4 and it gave me like .02 more per card lol
Try g2 with i20 (I've had some actually run that way, don't ask me why, or how, just happened on like 2 rigs with 7970s). I don't usually even mention it but seems to be acting the same as those systems did for me
No dice. It's funny how all of these cards can be so different/finicky.