Here in Spain it's completely against the law, they'll pull you over for it, give you fines, you can't get an ITV (vehicle road-worthyness certificate, renewable every two years) etc etc etc but there're still people who go ahead, and most are on a Streetfighter forum located in Barcelona.
Here's one of the guy's bikes, one of the few who has an FZR. (Most go the GSXR1100 route). I haven't met him in person, but I'd like to!!!
Here's his cardboard mock-up:

And the finished article (well, so far):

Some of the best sheet ally work I've ever seen, (excepting the the ally tank on mine)!


John