My marquee letter works! Keep reading below.
My Eagle files worked out well and I was able to make sure my circuit had no fly wires. I did originally think that components would be interchangeable when laying out the board for my letter (so all resistors the same & all LEDs the same), but this was not the case. I ended up needing to redo my layout a few times to get the resistors and LEDs in sequential order.
After spending some time at the Othermill, breaking a bit, and soldering for hours....
Yay! There was a resistor that wasn't fully soldered, which is why one LED is off, but I fixed it. And for my ATtiny85 board, I was able to get things pretty compact. I wished there was a way to dimension the holes, but I ended up kind of placing them by eye since I couldn't find a tool to do it more precisely.
And then I had some issues with this one at the Othermill. Some of the holes were too small so they didn't get drilled. I had to redo it making sure that the holes were properly sized in Eagle.
I noticed that the black boards cut a little more cleanly than the yellow boards. I wish I had added a hole to panel mount my switch, but instead it is kind of floating off the board.