These diagrams may assist (and confuse) regarding your interest in wiring rear speakers on your SESG2:
See post 4 for the diagram for the SESG2: http://www.cvoharley.com/smf/index.php?topic=53364.0
This shows the audio wiring on a non-CVO Ulta: http://www.cvoharley.com/smf/index.php?topic=53364.0
You'll notice the wiring diagram for the SESG2 includes provision for rear speakers with the signal coming from the amp, and not the HK radio. Haven't seen a speaker kit for use on the SESG2 from HD yet.
You'll notice in the non-CVO Ultra diagram that the signals for the rear speakers come from pinouts 1,2,24 and 25 of the 35 wire connector "Ultra connnector." If you check the wiring provided in the fist link for the FLTRUSE and FLHTCUSE6, they don't use those pinouts for the rears speakers; instead the front signal is sent from the HK radio to the amp which splits the signal for front and rear speakers.
Finally, if you mounted HD rear speaker pods on a chopped tour pak, be sure to post pictures of the installation. Mounting a regual backrest on a chopped tp lid is fairly common; mounting HD speaker pods on a chopped tour pak may be unique; I'm sure I've never seen one--probably because the chopped tour pak bottom is, according to HD, 3" shorter than the King/Ultra tour pak.
Carl