For the very limited copy work I have done, I have a dual camera mount "bar" I picked up perhaps 30 years ago. About a foot long, it allows 2 cameras to be mounted side by side, about 3" apart, on a single bracket. The bracket has a standard screw mount with the screw hole about 3" from one end that I simply screw into my older tripod. The resultant setup looks like a "T" with one side of the "T" longer than the other. I then mount only one camera on the longer end of the T, which centers the lens about 8" away from the vertical part of the tripod. After adjusting the tripod head so the camera is pointing downward, I move it over the corner of my kitchen table and shoot away. Whether it's flat paperwork or an array of very small parts I want to photograph, it works amazingly well. I'm guessing the practical limit on my setup is about the size of a sheet of paper, but that's all I've needed it for.
Now that I've gone to an L bracket and quick releases, I'd have to either remove the L bracket from my camera or get appropriate mounting plate and clamps for the double camera bar to use it again.