just got mayhem industrial and am beginning to print out all the stuff i need. however, i am a little confused on the basing part.

first off, im using the 1.5" grid as i am a heroclix player. with that in mind....

what is the difference in the regular white basing templates vs. the white basing template with the concrete/street border? for instance, i constructed the hollywood flat from the BoM set and used the basing template with the concrete border just because it looked cool but after i did it, i wondered why i would want to use the plain white basing template instead.

so i pondered, and the only reason that the street border thing is on one white template and not the others is to accomodate the 1.5" wargaming crowd. is that correct? im getting ready to print off the basing templates for my warehouse, but am unsure of which template to print off. help!

You can, yes.

The problem is that you will have a "skinny" square running through the middle, where each of these four tiles joins up.

If you redid the four floor tiles cutting two adjacent sides on the red lines (and not cutting the other two sides at all), you'll be able to have a full 9x9 square grid of "correct" squares.

It's up to you if avoiding the "skinny" rectangular squares down the middle of each side is worth the reprint.

Either way...yes, you will mount them on the street-bordered tiles after you install your walls.