Here are some pictures I have collected of rear diffuser setups
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various01.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various02.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various03.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various04.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various05.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various06.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various07.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various08.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various09.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various10.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various11.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various12.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various13.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various14.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various15.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various16.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various17.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various18.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various19.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various20.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various21.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various22.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various23.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various24.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various25.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various26.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various27.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various28.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various29.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various30.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various31.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various32.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various33.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various34.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various35.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various36.jpg)
(http://bigmike.marlincrawler.com/images/areo/diffuser_rear_various37.jpg)
Sheet the entire underside of the car with plexiglass sheet. Can bubble form around suspesion components.