Hello Old Grey,
I know this is an old post, but I just bought a couple of these and found some errors.
- The board is .1" too wide the distance between pin 31 (mislabeled BTW) and 47 should be 1.3" not 1.4"
- I added the 6 GND pins in the upper left, and the ICSP pins on the right
- Bussed all of the added pins where needed MOSI, MISO, SCK etc
I have made a board from this part and it worked for me.
Here is the updated part with revised breadboard, schematic and PCB views:
Mega2560 R3 Pro Mini.fzpz (80.7 KB)