After making/tweaking a few of these by hand, I decided to make a customizer so that you can create whatever fits your panel.

Since many panels are larger than most print-beds, I took the same approach as some others and planned for use as squares but give you the option of customizing it with 3 or 4 borders to join them seamlessly.

All you need to do is:

• Pick your panel size (P2, P2.5, P3, P4, P5, P6)
• Select how many LEDs per row (8,16,32,64,128) (square dimensions- see notes below)
• Pick your desired wall height (3mm works well)
• Wall Width (Customize this based on the size of your array and your 3D printer)
• Borders (3 or 4) (See below)

For wide panels (e.g. 32x16, 64x32, etc.), print one with 4 borders and 1 with 3 borders.
For larger arrays, use 3 borders for all panels in a square array. For square panel configurations, 3 borders for all. If you're advanced enough to do something different than that, then you can figure the border thing out for yourself.

I'm not marking it as a work in progress because it customized well in OpenSCAD, but please let me know if you experience any issues so I can resolve them. (I know the LEDs per Row isn't displaying properly. I'll fix it when there is something else to fix.)