I know I said that the next step was prototyping, but a few things have interrupted.
I orderd the red/green LEDs from Futurlec and wen't back and forth with them about the items being out of stock and what would work to replace them. I finally cancelled the order. As I also noted in the design, the MAX7219 really wants common anode LEDs so that we can have the points map to segments and the banks of LEDs map to digits. It turns out that it's a bit of a challenge to find 3-pin RG LEDs that are common anode. I finally found some made by Bivar and sold by Mouser. The Mouser order took a whopping 4 days to get to me.
Changing to common anode meant re-working the schematic. Eagle gave me some grief, connecting things to a bus that I didn't want connected. I had to offset the LEDs to avoid that problem. *sigh*
Next we'll work on the software drivers for the two display chips.