^^Joe@ptech is going to find that out real soon
Now with the rear bar.
Turns out on the 535 theres several sizes that the car comes with depending on options and if its RWD or AWD.
535i standard rear bar is 13MM
535i Msports rear bar is 14MM
535xi standard rear bar is 14MM
535xi with EDC/DDC rear bar is 15MM
I did not check this for the 528 or the 550 but you can easily do it with realoem.com
Since my car comes with a 15MM rear bar I will go with the 18MM F07 550GT's rear bar for a 3mm increase. Looks like you will also need to purchase new bushings with bigger internal diameter to hold the thicker bar. Hopefully thats it.