While there is nothing inherently WRONG with a cantilevered sidewall, some times this trick is used when Stock class racers are not allowed to fit wider wheels. you can squeeze a 225 on a 6" wide wheel but it's not always optimum. most 225mm tires recommend a 7" wide minimum rim.. you will get a slightly rounded contact patch and it makes pressure tuning a bit more difficult. but it can be used to add grip to the front in a pinch.

remember the first number in an aspect ratio size is the section width (total width), and since we all have calculators we know 225mm is 8.8 inches. so you're going to have 1.4 inches of cantilever. once again not completely out of the question, but less then optimal.

Personally I doubt your going to see a huge advantage unless your stock class auto crossing or road racing and can't correct an under steer condition via other methods. but if you want to.. check your wheel width, 6" or bigger you can, if it's a smaller wheel then I'd try not to do it. the difference between a 205 and a 225 is just under 1/2 an inch in total section width on each side. so check your clearance between your strut and current tire if you have .5" or more of clearance you should be okay.