strengthen ...???...on a micra???
so a couple of tooth picks and half a stick of celery should do it.
i mean theyre pretty flimsy as it is, but taking the back of...shouldnt do much, especialy if you do it on a 4 dor, you can weld the back ones shut.. on a 3 door...just wack in a roll over bar like on a Hilux pickup..lol