So there is currently no way to do it with cgminer?

And my card is not OCed, can I raise the speed without OCing it, or is that the only way?
In my experience that's not a cgminer problem (using -I d for sha256d like Bitcoin works fine), but a scrypt problem: sha256d barely uses the RAM of your graphic card but scrypt uses it heavily so it probably interferes more with other programs using the graphic card.