I have seen those Plano containers a few times at Academy and Cabela's. The bottom part is just as flexible as an ActionPacker (if not more so) and I must say that I wasn't really impressed by the amount of interior space because of all the indentations made by the molded shape.
However, I did find these 'airtight' containers made by Iris USA at Cabelas...
http://www.irisusainc.com/p-590-sia-760d.aspx
http://www.cabelas.com/product/Iris...cts&Ntt=IRIS&WTz_l=Header;Search-All+Products
Except for the 30" length I really like these. The $40 price isn't bad. The tops have indentations for the feet molded into the bottoms so they stack very well, and they have a foam gasket in the lid. The bottom part feels less flexible without its lid than either the Plano or Rubbermaid containers. I may use these instead of 24gal ActionPackers if they'll fit in the short back end of my FJ. Wish they also had a smaller 8-10gal version.