My car isnt lowered and the fronts touch the arches with only myself in the car!
And even with my 30mm drop,the rear has touched the arch twice on bad roads with 4 people in the car (Only slightly though) But you'd probably have to remove the arch liners to go 50mm or lower!
you bottomed out on 30mm? did you have Sports Suspension on the original setup? I can check via VIN number