I know
but I find it really cumbersome, especially if you want to be ready to slow down the game, like when you're entering dangerous areas (ports and stuff). Isn't there a datafile that you can change?
But It isn't such a big problem.
I've got another question: what slows down your system the most: having the "High Quality Textures" turned on or a high paricle density? (it's in the video options)