This may not exactly help, but it could be a potentially useful tangent. I've done the Stereo Mod on both my X-files and Star Wars Trilogy. With my skills, I usually order at least double of everything needed. You may want to do the mod, and see if you get output on the new channel.
http://www.pinballnews.com/learn/speaker/index.html
Good luck, and let me know if I can help in any other way.