I just bought a set of these "SeaSuckers"
They work awesome and grab some attention on an FR-S. The concept of attaching a bike using suction cups can seem sketchy but they're a well known company with no sign of ever having any accidents.
Saw a review on Slowtwitch.com (triathlon forum) where a guy with a Viper absolutely loved these things.
couple minutes to install and seconds to take off. Store easily in your trunk when you don't need them.
http://www.seasucker.com/product-category/bike-racks/