Hey, 05Train. I just saw this thread, and I did just what you're talking about. I have a FLHTCUSE8, and made the TourPak detachable, installed the BT4180, BT7.1 speakers in the fairing, 7.1 pods on the TourPak, and a Sony head unit.
The reviews are mixed. The fairing speakers are a huge improvement over stock. I can hear mid-range and upper frequencies pretty clearly at 75 mph, but bass notes are still inaudible. Maybe that's the best we can expect while riding on the open road, but even parked, the bass is not that great. I've cranked up the EQs on the iPod and the head unit, and the bass is just not right. The speakers are in phase (I've checked), and Brian at Biketronics couldn't help. I wouldn't be concerned about weight too much. The 7.1s are virtually the same weight as the 6.5 HATs. Any good speaker will weigh more than HD's junk speakers.
As for the rear pod speakers, I don't know what to tell you. They work better than stock pod speakers and definitely work way better than speakers in the bag lids, but again, they are hard to hear while riding. Plus, the bass isn't audible. I never ride with a passenger, so space isn't an issue, but the BT pods are bigger than the stock pods, so if you have a BSR who isn't really, really skinny, she won't be comfortable getting her behind crushed for more than a few minutes. The bigger speaker pods also make the TourPak harder to put on, but not a big deal. Finally, the connectors for the rear pods that Biketronics provide are incredibly cheap units. I'd be embarrassed to sell such garbage.
I'll try to look for pictures I took during the install. Good luck, let me know if you need more info.