One suggestion for the SPI header. If you print out compiler defined variables MISO, MOSI, and SCK they print out pin numbers as follows: MISO 74, MOSI 75, SCK 76. I believe these are the Digital Pin numbers for these three pins on the SPI header. Variable SS is defined as 10 and that is D10/D77 as you note correctly for SPI-CS0. Could these three Digital Pin values be added? Thanks for your consideration.