While I'm on this never ending search for inspiration for my own build, I came across this CRX from the one-make team, Vent Bull Dogs. Could this be FF rear-diffuser perfection from Gunma/Kanagawa areas?
Bonus - Since this post is already focused on the CRX's rear, here are a couple more photos on topic. One is an update of the previously posted Challenger Auto CRX build (that rear under spoiler is outrageous). And the other is of the famous SS Works CRX seen most recently at I Heart Honda 2009, which needs no description to depict its awesomeness.