Bob Brock sent me a great photo of these huge bunker blocks the way he built the greenhouse.he does things big. his precast blocks are 1' thick, x 4' wide, 8x tall. he sets them on 4' edge here His panels weigh 1500 to 2,000 lbs. and required a crane type machine to lift into place. He also used rebar-as you see here, , but only cause he had some to try- he does not use it now, PC does not stick to it as we all know. You will see a grooved edge- when he uses a steel form to cast a block, he places a pie of PVC pipe- cut in half- on each side to make a C shape. when he sets up the block he adds rebar, and pours a cement slurry inside the matched grooves, and makes a core of cement as required by his code guys. I was understanding he stood the dry panels up to be 8' tall, but here they are on edge. it would be hard to pour wet cement horizontally, so he may have changed how he fixes the panels. Mike MCain did a gang panel forms,, similar size as Bob's, and he made a long tall "breadbox-- with ply sheets spaced evenly and poured in his PC to each for, let them cure, and than has slices like bread-- only large panels.