Need help in German trench construction

[NATO]

Oh, where to begin. Well there is a rifle range going up in NC and we want to put in a WWI style trench line. My personal concern is the reveting, I really don't want a cave in during a match. From the pictures I have seen it looks like there are 2 main type the wood board type, and the tin roofing material. Both seem to have the wood "posts" to hold them up. How deep are these sunk into the ground? What has proven to be the least maintenance intensive? What seems to hold up to water the best? What are the design differences in the German and allied trenches? Any diagrams, pictures, manuals would be greatly appreciated. I looked at the GWA requirements for the trenches, it gave general guidelines, however I need something more along the lines of nuts and bolts. I was looking for a reenactor unit in NC to contact but as of yet have not been able to locate one.

Thanks in Advance

-NATO