it doest matter the scale. i found that different printers will print differently. The easiest way to do it is to print a few copies at different scales, then take your dash apart and see where it has to fit. then print the one that fits best. This is most accurate. You can tell how close you are because the solder pads are supposed to be exactly 4mm apart per led (4mm square).

I dont have a picture, but a good cut will drop right in and stay pretty snug. I used a dab of hot glue just to make sure it doesnt vibrate. The power will go in the back, you'll see it clearly if you look at the back of the ribbon PC.

Print one side, transfer, drill holes. Use pins or thumbtacks to line up the other side.

 

That's amazing. Does it dim?