I've got a backyard project that needs to be done as cost effective as possible. Its a double retaining wall. The problem is there is a third block wall on top of the two retaining walls, so it has to support some weight. Attached a diagram, kinda sloppy, I apologize. I'm leaning towards two short cantilever walls, however I heard there are lots of calculations involved. How do you figure out the width and slope? footing? Better ideas?