My tiles are dead-on width wise, about 1/16th short height wise. (HP All-In-One C4480)

Is this problem localised to the tile .pdf's? Is it a consistant innaccuracy with all of your users/brands? I ask because the first thing i thought of when i figured it out was that the printers may be slightly compressing the tile .pdf's because of the two small banners above and below the tile itself.
Perhaps combining the two little banners into one or eliminating them altogether would stop the compression effect.

Something tells me you guys have been over this a thousand times, and there isn't much you can do about it Dave

I have an HP 6540 (or 5640 ... can't remember off the top of my head) and I have to set scaling to 100% when I print or else it also prints out whacky. You might try that instead of scaling = none.

Print at fast draft setting to save on ink while you figure out the scaling and run your test prints.

Both of my HP's are about 1/16" short in the height... I copy the images and rescale them in Word to 1.1" and it prints almost perfectly.

That's not a bad idea. I thought about turning the .pdf's into jpegs and resizing them in "paint" (i do that anyways with textures to create my own patterns so i'm used to it).

Another thing i noticed is that if i print the files "letter", "scale=none" and "borderless" they come out excactly 7" tall, but about 1/16th" too wide.
It might work out to just trim a bit of the borders off the wide edges of the tiles and alternate them when laying them out. That way the grid will be complete.

For now, i just lined them up in the same orientation as they printed up and they fit together fine. I built a test bunker using my own folding technique on it's own base and it matches up with the board AOK. I'll just have to be careful with my measurements when laying walls and etc out on the board

I guess if you never use your printer for card-modelling you would never really notice the subtle inaccuracies of your print jobs... Dave