Yet another Autocross question (tire sizes)

I prefere to run Kumho tires during events. Running 225/45-17 Victoracers, but they are down to the cord. I would like to run V710's but they don't make them in that size. The next size I can get is 255/45-17, will they fit? From the research I have done so far it looks like 235's are the largest I can go in the front, and 255's in the rear?