we bought our ibiza which had been stripped to the extreme and things that had been removed included..

dash, all interior plastics, and carpets, rooflining, sun visors, seats, bootlid lifters, traction control removed, air con removed, inside of doors cut out, window motors removed, all underseal and sound deadening, every seatbelt, most of the wiring that wasnt needed, to windows, rear heated screen etc

we weighed in a 920kgs and have prob put about 150kgs back onto it with all the things that we needed

removing glass and putting perspex will get rid of quite a bit, sound deadening is quite heavy though a mission to get off!