There are pads to place 3 "extra" LEDs on the rev 1.0 boards. Those LEDs are available to add a colon for clock type displays and a decimal point for float values. They are driven from an extra column on the display driver. For rev 1.0, I just put SMT pads along the right edge of the PCB, with the intention of soldering the LEDs to the pads.

This did not work well. It was kind of an afterthought anyway. It was difficult to get the LEDs positioned with any accuracy and it was easy to pull the SMT pads off the board along with the LEDs.

The solution to most of the problems was to widen the board slightly (.050") and replace the SMT pads with through hole pads. The mounting is much more durable, the LED lead dress to get them in the right place is easier, and the vertical LED placement is pretty consistent. The rightmost LED is a little wild on the placement here, but I was experimenting with the lead dress for the colon operation and did not get the LED re-positioned well.

The new LEDs look a lot better in this use situation, as they give a well defined dot that looks more like the display pixels than the old round dome mini LEDs that I was using on the R1p0 displays.

The board to board spacing is fairly important to get things looking good. The pixel to pixel spacing on the displays is 0.100" and between the two displays on the board, the pixel spacing is 0.200" The decimal point looks OK if the board to board spacing places the adjacent display pixels are 0.200" apart.

With 0.200" spacing, the colon visually smears into the characters and looks bad. Placing the boards on either side of the colon so that there is 0.400" spacing looks much better, but makes the LED lead dress a little more difficult. The LEDs for the colon need to be spaced about 0.150 to the right of the display module and the height flush with the top of the display modules.

All told, the rev 1.1 board is an improvement and I am happy with the design now.