I had the same problem with my rear Turbo twists as the previous owner had bought Turbo offset wheels for my narrow body car, when I lowered it the tyres touched the arch lips.
When I took some measurements the problem was the thickness of material left between the wheel nut seats and the back of the wheel after machining, this would have been too thin and could have failed. This will also cause issues with the wheel stud lengths as they will bottom out in the wheel nut. You need to be really certain that there is enough strength left in this area after machining before you attempt it.
If it is possible (and I think this is unlikely) then the machine shop that carry out the work need to use a DTI (Dial Test Indicator) to ensure the wheel mounting face is perfectly true before they start machining, if they don't then the wheel will wobble and be difficult to balance.
I ended up buying new rear rims as it was the only safe option, sold the old ones to a club member who wanted to make a coffee table out of them.
The other option you have if the tyre is rubbing the arch lip is to have the lip rolled under, as per the RS model cars, by a body shop. This may be a cheaper option than buying new rims, but may still not completely solve the issue.
