It would be my guess you could stretch them because the sidewalls are practically bomb proof. I was able to stand on the tires (vertically) with no rim in them and they did not even bend hardly at all. After driving on them for about a month now I can say they have a much stiffer side wall than the Falken Azenis! These things handle VERY well and are extreemly consistant!
Just for legal reasons I am not saying that you should stretch them, I was just giving an opinion.
Tom