How can I increase Power Target (within official limits)?

I would like to increase Power Target for my card (GTX 680). Currently it underclocks so bad sometimes that I even do not get stock boost frequency (it is Gigabyte OC card). At the moment I think I’m on default 100% Power Target. Stock BIOS allows me to increase it up to 111% (260W). But how do I increase it in Linux? I googled, but all I have found is -pl argument for nvidia-smi, but if I try to run “nvidia-smi -pl 260”, I get this error:

Changing power management limit is not supported for GPU: 0000:01:00.0.
Treating as warning and moving on.
All done.

Please note that at the moment I’m looking for a safe way to do this (no flashing, no hardware mods). Or setting Power Target is not supported yet?

I would like a power target too, seems odd that Windows applications got this but it’s not available in Linux.

Making it available with nvidia settings when overclocking is enabled would be the best.