I used the JC41 in my setup, and it's in the downtube, just above the bottom bracket. It has cables going to the battery and rear derailleur, with a spare slot for a front derailleur, and then a long cable which goes from it to the left shifter. The other cable on that shifter goes to the right shifter, which also has a connection to the bar end junction box.
I used the JC41 in my setup, and it's in the downtube, just above the bottom bracket. It has cables going to the battery and rear derailleur, with a spare slot for a front derailleur, and then a long cable which goes from it to the left shifter. The other cable on that shifter goes to the right shifter, which also has a connection to the bar end junction box.