Best bet if you want to realy go wider is just get wider rims...I'm not sure the offest of my rims, but you can, when you get new rims, fit, as i have fitted them, with the right offset go as wide as 18 by 9 (that's 9 inches wide...hehe) Its just all in the right rim and offset. IDK about cornering but it sure helped with wheel hop and spin during launches.

My old shit rims were very narrow with alot of sidewall...not good for cornering...you may want to consider that...a lower profile tire...i do believe that may help a bit by reducing the side wall, but don't take my word for it.. ...low profiles tire are harsher on the ass though...

I love my car...
I love Horsepower...
I love reliability...
So why do i own a DSM again?