I know there's a good amount here who either a) can't dedicate themselves to hanging everytime they go out b) can't justify spending the money on a TQ/UQ combo and are trying to save money using pads. This is especially for you.
When I got my kick back together I tried to correct things I didn't like about my last setup and use my knowledge to put together the most versatile, cost-effective, system I could. Make one purchase and make'em count.
First off, whatever under insulation you use, it's the most important to keeping you warm. Especially in a hammock. I'd always take something that's capable of the worst case temps +5*. In my case, I got a downmat so I could save some weight on the SB without having to jump up another 100.00-150.00 going to 800 FP. That's an expensive lb.
This is a modified mummy, which is basically a rectangle bag with rounded corners. Really good option for heavier guys. Being as I'm not, it's very spacious, I can kick around all I want and wont accidently break my seal. I've slept in the fetal position on my side in it. Used it down to 21* (it's a 30* bag, under-insulation)
Also, it puts all the down on top, efficiently using your top insulation. It's also got a pad sleeve. I think this is a welcomed option ESPECIALLY in a gathered end vs. trying to get it to stay between the layers. Its even got a "wedge" overlay on the pad so there's NO GAPS. That was 650fp down btw.
Speaking of the down. It's hydrophobic. So all that "should I get synthetic or down" you put yourself through, don't bother. It's weather resistant shell coupled with the hydrophobic down.. can let go of a bit of that down paranoia and with a pad, you're looking at a pretty water-resistant set-up. Also have a set-up that's good in a hammock and on the ground.
Even if you get the best/lightest pad available (which can be found for 200.00) with this bag whcih you can find for 154.00 at Moosejaw on sale (I googled a coupon code for another 10%), for 334.00 I covered 4 seasons and hammock and ground for down insulation that's as "waterproof" as synthetic. Total of about 4lbs pad+bag for me. If you use reflectix as a pad outside of winter you're at 2.5lbs and down to 150.00, with enough reflectix to cut 3 more fullsize pads. Using them in the padsleeve they work perfect and are very comfy on the ground as well.
Something to consider when trying to get comfortable for cheap. Use this in a GTUL for 20.00 and get a HHF from JRB for 60.00 and you're in the trees in a 3 season waterproof down setup for 230.00. Or you can scavenge some tyvek and get back down to 150.00.
Was just up late and admiring how well my setup treated me this past weekend and happy my plan came together. Hope it helps out others who can't justify UQ's whether price or utility.
Guess I'll try to go to sleep again.