Dom, all
I have experienced the twitch thing with all of my 12th cars. I find if I can really wipe down my front tires well before the race the twitchy is reduce greatly. Just giving them a quick wipe with a towel doesn't work that well, I spend nearl 2 full minutes on the front tires alone. I also fond that cleaning my tires with motor spray helps to keep the grip for longer in the race.
Chris.