This is for the riders on a budget that are looking to get a little more weight in their boat, without taking up space.
We had a softside water bed that we weren't using, that came with individual water tubes. We were gonna junk the whole thing, until we realized the tubes could be use as fat sacs (sort of)
They normally run about $25 a piece, but you can find these on Ebay and craiglist for cheap.
What we did -
We filled the tubes and laid them lengthwise in the compartment in the floor. Each tube weighs about 1oolbs, and we could only wedge 4 of them in. But it made a noticeable difference.
I'll post our pics soon as I can...