Hello! For track use, I tried both a 245 square setup (Yokohama AD08RS) and a 235 square setup, as well as 235 front with 225 rear (Yokohama a052). The last one is better, the car feels more agile, and it makes more sense on a FWD car with such low weight in the rear. Also worth noting is that they are very different tyres.
9-inch ET45 is quite aggressive. You’re right, my car has a widebody to fit the wheels, and on the inside there isn’t much room left between the wheel and the shock.
You are free to do whatever you want; in the end, if you don’t try different setups, you won’t know which one suits you best. If I were you, I would run 225 or even 215 on an 8" wheel if it’s a semi-slick. With 235 UHP tyres it's okey too but I would still go 225 UHP, you may feel the steering isn’t as sharp as with 225 semi-slicks.
Hope this helps. Again, I would suggest trying different setups to see what fits you best