I know with the +20 offset that 5zigen offers you would Definalty have to roll you fenders. With 18mm further in you might just have to bend the lip out of the way.
There is an excellent thread on Zilvia.net of all of these rims,tire sizes, suspension set ups, big brakes, and alingment setting that will work.
Just remember if it does not fit there are 2 solutions, more camber or a bigger fender pull.
Which lip are you talking about? The fender lip? Or a lip inside the fenderwell?
EDIT: K I know what you mean now.
These 9’s fit just fine with a 235/45 on them. I can’t see an extra 10mm of tire on each side making much of a difference. Plus the 255/40 is slightly smaller in dia (0.3").