Growing upside down?

[AJ Drew]

Have grown upside down before, but the containers were small decorative things.  Sure you know the type, bowl shaped lined with burlap.  Most turned out small and I had to water them every day.  Thinking on building a second high tunnel.  Looking at the first, the center is maybe 8 foot high.  Plants are maybe 4 foot high.  Seems like there is a bunch of space not being used.  Kind of wondering if I were to use five gallon buckets up there and painted them black if i wouldnt get more growing space and create a row of heat sinks.  Hmmm....  Thought about building wood boxes into the thing but if it restricts too much light, i want to be able to remove them.