May give people some ideas, although not very subtle:
http://www.topgear.com/car-news/modified/bulletproof-bmw-z4-isnt-bulletproof-deranged
http://www.topgear.com/car-news/modified/bulletproof-bmw-z4-isnt-bulletproof-deranged
http://www.z4-forum.com/forum/viewtopic.php?f=23&t=82202