9x18 backside.... is possible?

Hi all I'm new here... I've just a question for you slk-experienced: I want to put on my 200k 18"alloy wheels. Luckily a friend of mine has an alloy wheel factory so i can have them at around 1/3 of the ordinary price but... on his catalogue there aren't 0,5 sizes, just 8X18 or 9X18. So,in front there shouldn't be problems since i see some of you are using 8,5x18, i'd like to know if someone of you is using 9Jx18 rims on the back side (with 235/45 of course), if it's possible without modifications or should i use the 8x18 front and back?

anticipately thanking for your answers

Flavio
200k Obsidian Black/black Leather[]