I'm going thru the same GRIND issue, I have 18x8 +48mm. I lowered the E more on KSports and now the trailing arms grind against the inner edge of the rim during road bumps. I've been told, raise it back up, put spacers, heat/sledgehammer the affected trailing arm area (to clear some space), or get wheels that have a smaller width and smaller offset range.
Thanks for the info!
It's been a while since I saw this thread!
I ended running the wheels, had MAJOR grind and rub, bought 20mm spacers to puch them out and now will need to send my teins in for an overhaul just like you Darth. Unfortunately, I learned the really hard way.