Hey man, do you by any chance have a picture of the hre under the car?Here is some information I got from a person who had a very low and stanced e9 before, I asked him directly many years ago when my plan still was to go with big wheels.
"The BBS were 18x8.5 et13 and 18x9.5 et13.
In the rear, you cannot fit a wider wheel, nor a 9.5 in any other offset. It clears both the inside and outside of the fender by about 1mm.
When I swapped to the HREs, I went with 18x8 et10 and 18x9 et10 for a little extra room, and I was glad I did. Those are the sizes I recommend if you're going for that look"
Cheers,