It's funny how people are so scared to modify there car to make any upgrade work. And people think it's safe to cut up a bumper support to fit a big ass intercooler. Anyways I like the idea, one thing I would have added to that was to add another insert cross ways to make an H pattern. That would probably rid of any side to side movement of the arm. It just looks like you boxed in the arm.
About the spacers, first when you add an aftermarket set of rims to your car you are going lugcentric instead of hubcentric. So no difference except the load being put on a different part of the stud. The fix for that is get a spacer that matchs the diameter hub and stud. Then you have to worry about the movement of the wheel and spacer, simple fix here just screw the spacer to the rotor. On my old fwd I ran weld racing wheels 15X9 with a 4" backspace. I took my 1/8" spacers and drilled them, then I put a tapered screw through the hole so it was flush on the spacer. Running a 26X8.5 slick I never had any issues with my lugs working lose. Maybe I wasn't makin enough power. I guess it's all in checkin your stuff before you drive the car.
