Ok ... have a few mins free to explain.
Spoke with HD tech install and he explained the issue as two-fold. I'll state the problems and then my proposed mitigation:
1. As Carl projected - the fact that the SESG2 connector 28A (HK radio) is in use via the iPod interface, HD could not say that the speaker pods will fit as they require the use of that connector. Note that the requirement for "seamless" installation (whatever that means) states the non-ultra overlay harness is a mandatory purchase. This harness plugs into connector 28A on the HK unit (right side of radio facing the rear of unit). Since 28A is not an open (or unused) connection HD cannot say to remove it for install of the pods.
Mitigation: Simply purchase the non-overlay harness and de-pin the stock SESG2 iPOD signals from the 28B connector. Re-pin to the corresponding pins on the overlay harness for the 28B connector. I don't see any problems here and I am going to perform this regardles of issue 2:
2. HD also stated that the SESG2 audio system is a "1 ohm speaker" system. According to the tech, all speakers installed on the SESG2 system are 1 ohm nominal impedance (including fairing). They could not recommend (or state that) the 2 ohm (rated nominal) speakers in the speaker pods would not induce a "degraded experience to audio quality". In my opinion his explanaition and statements are EXTREMELY doubtful. What he meant to say is that the SESG system is a 1 ohm
load system. If each of the 3 drivers (per Left or Right channel) were tested at 1 ohm nominal impedance - the amp would see a total load (per channel) of 0.25 ohm (1/4 ohm). I find it hard to beleive that an amplifier could have such discrete circuitry as to discern a 0.25 load as a not being a full short circuit - It would cook to flames rather quickly

. Remember - all 3 speakers per channel (left OR right) are wired in parallel. In order to obtain a 1 ohm "system" (total load per channel)... each individual speaker would require a nominal impedance of 4 ohms (4 divided by 2, then divided by 2 again = 1). Again (imho) I see the MoCo as "cheating" with the specs - yes it is probably a 100w per channel system. Unfortunately it is probably only a 25w per channel amp (RMS verified at a minimum of 4 ohms load). Mitigation to this problem becomes more involved.
Mitigation: Mitigation here becomes very involved without replacing the amplifier (what I plan to do). In order to use the pods
as designed - it would require hooking one pair of speakers in series with another (as opposed to parallel). You would need to run the negative lead of any one speaker to the positive lead of the pod (I would suggest using the speakers in the lowers) - then run the negative lead of that pod back to the negative lead of the original speaker. Repeat for the other side. Very involved if you ask me - but this should keep the total load in check and allow the stock amp to work. Keep in mind that the output of the amp will diminish a bit as the total load on the amp will have increased slightly.
Dealing with issue #2 using the stock components is just too much work for me - I'd rather solve it via better components, better design, and better sound via aftermarket. Kudos to HD for (once again) taking the path of most "fawked-up" design possible for something that could have been really great.
Anyway ... I hope this helps to understand the nuances and intracacies of the SESG2 audio system a bit better. Thanks to Carl (Harleypingman) and oliver105 for posting the wiring diagrams. THAT is a benefit to all!!
Rich