Just completed the install in my own ToM.
I had a little trouble with the breakout board because my J120/J121 GI string connectors had one fewer pin than the breakout board. I was having some difficulty with the Inputs matching the Strings as I expected, so I started playing with the connectors.
Ultimately, for me, it seemed to work right once I attached the J121 string to J3 and the J120 string to J4, with the J3 connector married to the left side of the string connector and the J4 connector married to the right side.
I realize none of this should matter, but since it works, I figured I'd post it anyway! Here's a photo: