I don't think that if you get 235/75/15 tires on your Sporty anyone is going to even notice.
Unless you park next to another Sportage or if you have to take it in for inspection. And if you take it in for inspection then change the tires back to stock first.
If it sounds a bit shady, sorry, we don't always have legal vehicles up here in Alaska. I'm not all for doing things illegal, but who is looking at your tires every day? As long as they don't have big white letters saying the size on them, then you shouldn't have a problem. But don't let me corrupt you with my evil ways.