The flat pack could be a winner. It's all about weight. I'm going to check that out.
They definitely seem like the right choice if you have jars (or jar-like objects). I haven't explored, but I got the feeling the flatpacks aren't resealable. Might be a case where the most cost-effective approach is paying once for jars, then buying flatpacks. Obviously, you know your situation better than I do; I'm just doing the equivalent of thinking aloud.