OK, here is how you remove the rear seat belt. It is a little bit of a pain and not worth the effort if this is all your doing. Since I am installing the roll bar, I already had to do most of the work so no problem.

You need to remove the B pillar and then remove the lower rear panel. Then you can see from the photo where the belt is. There are three bolts, 10 mm I think, that you need a 8" extentsion to reach easily. You can just pull back the insulation and it's quite easy.

Don't have exact weights yet but it isn't a lot, 2 lbs maybe. PM me for more details.