Nobody said you can't fit 245s on the stock wheels--you just won't get the maximum potential out of them like you would with 8.0 to 9.0" wheels.
If you like how it is now, you should see what it's like when the tires have proper lateral support!
-Ed
EDIT: PS--Case in point, when Subaru made the minor updates to the Impreza WRX STi the second year it was available here in the U.S., one of the changes was widening the wheels a half inch, because they found that handling improved sufficiently from the increased lateral support to warrant the part change (adding new parts to the catalogue entails costly logistics).