I recently purchased a good chunk of the DSP upgrade kit (I didn't need the E-Stop or other accessories) and have it almost all wired up. The machine homes out correctly (as far as I can tell). Many thanks to the users on the forum for their knowledge and willingness to help!
Though, after searching the forum and finding that awesome wiring diagram and following it to the letter, I'm still a bit confused:
I have no idea where exactly the laser tube cathode goes. Here's a picture of my laser power supply:

The anode is wired into the back of the supply. The inlet on the left has four slots labelled (from left to right) L-, FG, AC, AC.
The next has six slots: G, P, L, G, IN, 5V. I know this is used to hook up to the DSP card.
The far right inlet has four slots: 24, G, 5V, L. Could the cathode wire go into one of these slots?
Thank you for your assistance!
-Jordan