I love the Earthtainer, and I think it's a great method of growing. However, I find the method of making them to be laborious and (honestly no offense intended) a bit wasteful.
Just curious - why don't more people use single container methods? There is a guy out there called "Albo" who makes his with corrugated drain pipe. (the slotted kind) Instead of 2 containers, he just buries them at the bottom like a septic field. I have made many in this manner, with the ends capped of with regular old non-metal window screen, and something to tie in-between corrugations. (to keep the screen from slipping off)
Larger containers can be made from 55 gallon poly drums, with the top 1/3 cut off, slitted in the side, and pressed down into the bottom 2/3 of the drum, or the drums can be cut in half, and the corrugated drain pipe coiled in the bottom.
I'm going to post a link here to Albo's site. If it's inappropriate, feel free to remove it. But I will attest to the fact that this method works VERY well, with less waste, and less cost.
http://albopepper.com/30-gallon-tote.php
Making a 5 gallon SIP is limited only by your imagination. I made one the other day using solo cups and the lid from a plastic lettuce box (all recycled) as the reservoir.