NOS moldings also take 6 clips per side, & 12 screws per side. 6 of the screws hold the clips in place underneath the door, the other 6 screws secure the molding to the underside of the rocker panel.
I guess you could get away with 3 clips per side, but I would either ask(demand) for more clips from the vendor you bought them from or buy some online. They repro those clips, so availability isn't an issue.
The way I mounted mine was similar to Bill's (Flameout) method. First I taped a line of 2" masking tape along the top edge of the rocker where the top of the molding will sit. Then I used more masking tape to hold the molding in it's correct position.
Use a marker to trace a line on to the masking tape from front to rear of the top of the molding. Next take one of the supplied clips and place it just below your traced line, & stencil a circle inside the hole of the clip. That's your drill spot.
I aligned each of the 6 clips directly above the lower slots where the bottom screws mount.
It's a fairly easy job.