Can I get some sensitivity advice?

First off I know the ol' adage. Just use what your comfortable with....The thing is I suck in general...have always sucked and I'm realizing there could be a small correlation. Like maybe I'd suck slightly less with a better set up.

I've been playing on high sensitivity my whole life...like way too high. I just realized all the pros, and most people who are good play on the lower end of the spectrum. I would have guessed otherwise. I've always been a wrist mover when it comes to M+KB typically because I have a tiny mouse pad. Well today I bought the giant mouse pad and I want to give this a try. See how much of a difference it makes.

I'm assuming those of you that do 400 DPI with 2 sens have giant mouse pads and move your whole arms right? Is there a general rule of thumb when using giant mouse pads like this? Do you want to be able to turn your entire body 180 degrees when moving half way across the mousepad?