I'm considering a 3 row vinyl raised bed against my masonry foundation. Does anyone have experience with this height? What spacing did you use for your posts, and how far did you dig your posts. I'm aiming for 3ft depth by about 13 ft long. I'm not sure if having three sides vinyl and one side masonry is an advantage or disadvantage for maintaining the structure of the bed. I've seen some kits available online 3 rows high, so I assume it's a fairly stable design.

Thanks in advance.