Oehler house shoring boards: plywood, insulation?

I've been planning some more additions to our half-buried home, and i think I may want to go with Mike Oehler's methods for this next section of house.

A few questions that I can't find in his books (I have the $50 and the greenhouse):

For the shoring boards, what sort of thickness?  I am assuming like 1X4s or 1X6s, but is he using thicker for the walls?

Has anyone tried like OSB or plywood instead of the boards?  I would be covering the boards anyway, so looks don't matter to me, it is a cost issue.  I would think that 2 1/2" OSB layers, staggering seams would be just fine.  What do you guys agree?

Anyone do this with other materials, like concrete for the posts, metal or panels for the shoring?  Wood is not as available in my area, so I may have to try a cheaper, local alternative.

What is the word on insulation? Do we insulate outside of the shoring, or best to insulate like 1 -2 feet of dirt (create umbrella)?

If I recall correctly, the boards Oehler used were mill ends from a nearby mill, and so were free for the hauling.  They certainly look like 1X stock in the pictures, although they may be rough cut, and so a little bigger than the 1X you'd buy at the lumber yard.  I don't see why OSB or ply would not work in place of the boards.  The thing is though, that Oehler had access to free shoring, and I believe the posts were cut from timber on his land and therefore also free but for the labor.  If you have to buy all of the materials, PSP might get expensive in a hurry.

I've occasionally wondered if it would not be possible to do something combining the PSP idea with earthbags.  I think the degree of shoring necessary might be excessive, though. 

With concrete, I think you could probably make the posts with sonotubes or similar forms.  I'm sort of down on conrete lately though, for a variety of reasons.

Doug

Abe, did you end up using OSB for the shoring? How many layers of OSB were you talking about here? I'm in the process of designing my Oehler style structure. I think I'd rather do that than mill a bunch of wood on site.

no, I used billboard tarp. Cheaper and easier to use. Check it out: http://velacreations.blogspot.com/2011/12/rapidobe.html

Very cool, thanks Abe!