I've got Eibach Pro Springs and a Milltek exhaust and even with my diet pie eating mate in the back it hits the rear beam over fast rough roads. Tested theory by putting gaffer tape on the rear beam and driving with the aforementioned mate - after the drive I can see witness marks on the tape!
As a result I don't carry passengers! This combined with having no boot (sub etc..), my car has all the practicality of a Westfield, except that without a top, the Westfield probably won't have an anoying rattle from the roof lining!!!
Still, I wouldn't give up chasing white lines and road imperfections while overtaking 'faster' cars!!!