Do you need the rear seat? Maybe you could do a rear seat delete and a longer seat bracket to slide back another 1/2-1"
http://ft86speedfactory.com/seibon-c...panel-493.html You may not even need to change the seat slide, I don't know if that is the end of the slide or the seat cushion stops it first.
You might check out some of the forums for other small cars and see if there are any hints or tips. Miata, del sol, s2000...