copy_and_mirror_data.ino

const uint8_t ppm = 150;  //pixels per matrix


//You can do something like this to simply copy the data to the other matrices as the first matrix is filled in.

for (uint16_t i=0; i<ppm; i++) {
  leds[i] = CHSV(random8(),255,255);

  // copy to other matrices
  leds[i + ppm  ] = leds[i];  //2nd
  leds[i + ppm*2] = leds[i];  //3rd
  leds[i + ppm*3] = leds[i];  //4th
  leds[i + ppm*4] = leds[i];  //5th
  leds[i + ppm*5] = leds[i];  //6th
}


//Or something like this to reverse (mirror) every other one.

for (uint16_t i=0; i<ppm; i++) {
  leds[i] = CHSV(random8(),255,255);

  // copy and mirror every other one
  leds[ppm*2 -1 -i] = leds[i];  //2nd mirrored
  leds[i + ppm*2]   = leds[i];  //3rd
  leds[ppm*4 -1 -i] = leds[i];  //4th mirrored
  leds[i + ppm*4]   = leds[i];  //5th
  leds[ppm*6 -1 -i] = leds[i];  //6th mirrored
}