I ran mine today at the regional at broxtowe.
I've been running so far with the pro spec car, and to be honest they're pretty damn close in performance. Shaun ran my old pro spec car and on our 'fastest' runs, we were only seperated by .05secs!! over the five mins!!.
i think on grass the car felt like it wanted to bite more going into corners, but as the grass wore down the car felt more balanced and was just as quick as my old pro spec car, and faster than other pro spec cars around me. I'll sort a set up out at some point and post it for people.