Sounds awesome. I'm sure that you'll figure it out, and when you do, please post pictures. Just to share your experience and accomplishment with other fellow Jeepers looking to do the same thing. I wish I could be more help, but I've never done anything like that.
But, upon looking at the description of the LOC it says that the rear and sub channel can be combined, not the front and sub channels. Maybe this is the way the LOC processes the signals internally and splits them. It requires the signal from the rear channel, not the front channel. Just a thought, not sure if this will help.