Cab Clearance Lights

I ordered 5 cab clearance lights today for the Mazda. I know a few of you guys have done this before so I figure to be on the safe side I'd better ask:
-How'd you space them out, what are the best measurements? I dont want to mess up and start filling in holes..
-How do you remove the headliner so I can run the wiring?

all i had to removed of the headliner to wire in the lights was just the first section at the windshield and its just a slip in hard plastic strip that runs the length of the windshield. once that is pulled out from its spot it gives you the first section of headliner up to the first sewn line. (something like 6-8 inches). and i do believe it really really helps to have both a pillar plastics removed at the time to make headliner pull back easier, and for running your power wire up your driver side a pillar.

also, when i wired mine the cab lights are powered by a relay that comes on when my running light circuit at the column is turned on, so if i turn off my park/headlights the cab lights lose power as well. and i have an interrupt switch on my a pillar near the top so i can independently kill the cab lights so i dont have to run with them on all the time when my running lights are on.

Thanks for the help. I'll get some pictures when its all done!
I might just get some cloth and put in a new headliner while im at it. Some numbnuts did permanent marker graffiti on it -.-

you can try a product called "goof off" to remove the permanent marker... or fabric/vinyl spray if the headliner is in good condition but just has some coloring on it... mine used to be gray... used the flat black fabric/vinyl spray paint from autozone and my headliner turned out awesome. took about 2 cans to get it completely covered evenly