I agree with all those suggestions, some of them I wonder exactly how much they'd do. I mean stuff like removing carpet underlay and soundproofing thats almost gonna be negligable, not worth it. I wouldn't really hesitate in how much paint I applied as the advantages gained as far as weight goes is nearly nothing. Of course depends how serious you are as every little bit counts.
Good thing this topic came up cause I have lots of questions about lightweight parts and panels for an XY, I might wanna do one up with fibreglass bonnet, quarters, doors, bumpers, boot, you name it and I was wondering about the how much weight these sorts of things shed.
ZC-CRUISER, the guy wants his car to go faster and you suggest to go a smaller engine, I should slap you. lol.

By the way, do you know how much weight can be lost by going honda seats?