I don't think your 7" wide rim will be too narrow for 225's. As I said, 225's on my 6.5" rim were fine.
Just for the hell of it, I pulled up Direzza Sport Z1 Star Specs in 225/50R16 on Tire Rack and it says they fit rims from 7-9" wide.
http://www.tirerack.com/tires/Spec.j...um%3D25VR6Z1SS