Nophead commented on the original Heptagonal Column that Skeinforge would not print a zero thickness face... so I made this variant to show how easy it is to adjust the thickness of the bottom layer to exactly the value you want!

To adjust the thickness in Sketchup, select the push-pull command, use it on the bottom face, and (with snap/precision set to something compatible) adjust the thickness to exactly what you want.

You can also adjust the thickness of those triangles on the side with the same method.

Most CAD programs should support this method, altho the command might be named something like Extrude, perhaps.

The only piece of information you should need is the minimum thickness you can print. If someone can give that value for a Makerbot, I'm happy to make an STL file with the right thickness for someone to test print.