With a 99 SVT and stock suspension, the chances of you rubbing on 225/50-16 are very low. Personally I love the way they look, they fill up the wheel well just a hint better than stock size. I have run two sets of different brands, and even loaded up, no rub.
If you want to see the numbers on just how much taller they will be, check this out:
http://www.miata.net/garage/tirecalc.htmlA lot of people have them and like them, do some searching.
Brian
99 SVT