You're a nut. Cody approves.
just a thought, I've got these 15 gallon plastic barrels here that are barley extract comes in. You could use them to fill with h2o and stamp the dirt down, or underneath the rolls in your track to require less dirt. They are 26" tall and 14" diameter.....so if you put them on their side they would be 26" across and 14" tall.
They are free if you want them.