How about using "tomatoe stakes" with 3 or 4 lids fixed at various depths? Or even bamboo? Then you just drive them into the bottom and your done. Could be put together on the water so you wouldn't have much trouble with space for transport. If there is a furniture factory or some other factory with hardwood stakes as scrap, you can usually pick them up for free. I have a truck load of them now that I have been trying to figure out the best way to use. Thanks for this thread, now I got me an idea.
Brian
Will fish for food!