If you are getting down to the nitty gritty in lightening up Nylofume bags are half the weight of compactor bags, unscented and very durable. The size commonly used for pack liners fit well for example in pack similar to an Exos 48. They are used in the exterminating business for bagging items when fumigating. Here is a link for an example. Many BPing sights will occasionally have a member buying in bulk and selling them off at their cost to help others. Thats how I got my hands on a few.

http://quantumtermite.com/nylofume-bags-20