I stripped my whole car from the rear seats (including them) backwards, door cards, seat belts, platic trim etc and spare wheel. Did it as I was sound deadening the lot. Out of curiosity I weighed some of the parts and you could remove 50-60kg of weight.
You will need to consider sound deadening as well if you are just going to remove the parts and not put anything back in as the road noise is painful when your car turns in to a hollow metal shell. Plus you will end up with some holes as you remove bolts and clips etc where you can actually see the road underneath.
Dan