C- Question: Over in your neck of the woods are there lots of available soil colors? My guess is some areas of the world are RE haven, others need pigments? Do the pros have various soils on site the mix in different soils for a course? The other prob I see with that is having to take all these soils to lab to be tested to pass building code. A white base mix and pigments seem like a better choice, but pigmentating the total thickness can get expensive. So can hauling in different color soils, and the embodied energy. I get a bobcat if it were available before I sent buckets up a conveyor belt. Scaffolding and and a mix bucket a fork lift could deliver to two sides of the building to keep the rammers ramming. The bobcat does the mixing. I'm still not understanding this "marine ply" ....I do know that here is plastic "marine board" some of which has an oil additive for skid plates on off-road vehicles made of UHDPE. It may make some cost effective light weight smooth forms now that you mention it, and they are stiff. Plastic shops sell 4 x 8 sheets in 1/4 - 1/2 thick, and they are stiff needing no stiffeners. A machine shop could lighten them up, creating machined in stiffeners. I used some vegetable oil on my drain hole block outs to get them out easier. Then I found out to just taper them. The way my surfaces turned out dirt would stick to the oil. Using OSB I really didn't have alot of sticking unless my mix was too wet, then it stick to my hand rammer. I used the rammer and shovel stick as a guide to get my water level right.