Powermizer: locking to specific performance level using xorg.conf option?

Hi all.
I bought a laptop with GTX 870M (with Optimus). It’s way too much GPU for my needs. I figured out how to switch to Nvidia GPU after login to desktop, but haven’t found any way to cap GPU performance to lowest level possible.
Can it be done? With xorg.conf preferably?
Thank you in advance.



Thank you so much. :-)