giroman,
The information mjb765 posted is one way to deal with SESG2's unique wiring; another is to simply add the missing 6B connector (which has been described on this forum) and use either the NUOH or 69200033 harness). As for modifying the NUOH, glad it worked for you. TIF2 (Rich) did so on his SESG2, and probably knows more about adapting the audio and wiring on the SESG2 than any HD dealer and, possibly, the MOCO.
As for the bracket mjb765 mentioned, here's the link to Scott's bracket:
http://www.cvoharley.com/smf/index.php?topic=61136.0Velcroing the module w/ zip tie to the bottom of the radio should work--I had my CB module mounted that way for about a year before getting Scott's bracket.
Suggestion only: next time you have the fairing off the bike, snap a few pics and post them. It's helpful to show how the NUOH and other wiring inside the fairing is routed--I know it took me several reroutes over time to get the outer fairing to fit easily on the bike after adding the NUOH, amp, etc.
Carl
PS: I'm not a tech or audio guy; just a civilian (i.e. I'm not in the bike business) who has worked with HD's wiring diagrams, installation instructions for various audio accessories, and parts books to make mods to my own bike.