Quote - I want to render a page, but I need writing on both sides, and different on each side, so I need to UV map the top and bottom.

Poser can't use double sided polygons, so I have to make a cube that is very, very flat.

How flat can I make it? Can I make the height 0.0000001 Poser units? Or will that give me rendering artifacts?

You didn't say which version of Poser you are using but if you have Poser 6 you can use
a no width double sided polygon.
Just go to the material room and put a check in the Normals_Forward box at the bottom
and that will get rid of the weird rectangles pattern.