You don't say exactly what it is that doesn't work... Do you mean the entire programme or just the speed cameras etc?

In any case I think perhaps your sys.txt line should read android_secondary_root_path="/storage/external_SD/Addons/iGO/"

I have "content" folder in SDCard root containing folders: building, car, dem, histspeed, map, poi, and scheme
I have "iGO/content" in device root containing folders: global config, lang, skin, speedcam, userdata and voice

In sys.txt
[folders]
has_secondary_root=1
android_secondary_root_path="/storage/6FB4-9A2C" (this must point to the location of your "content" folder)

This works fine for me and lets me share the SDCard content between different iGO versions on the phone.

Good luck with your efforts I hope you will be successful