I haven't seen the zipper he's using on the PL but I'm assuming it's the same one he uses on the bags and everything else and it's HUGE. I've gone through 3 of his bags (currently a zero bag) and a jacket. They all use the same giant zipper. For use in a hammock a quilt works better than a bag anyway. I don't think you'll really want the zipper.
Here're some photos of what I'm talking about. My apologies for the blurriness; my phone is my camera.
From left to right:
1.) A dorsal view of the liner, taken from the head end, of the poncho liner with the ties tied up.
2.) A ventral view of the liner, taken from the head end.
3.) A ventral view of the liner, taken from the foot end.
4.) A detail photo of the foot "box" ties, with a couch cushion inside to give more relief to it.
Please let me know if you have any questions. It's not hard; I just used shoelace knots to hold them together. They're not weight-bearing, so I'm not too worried about one coming undone (hasn't happened in about fifteen nights sleeping with it like this).
The insulation under you doesn't matter much; it's going to be compressed and not do much that your underquilt or pad isn't already doing for you.
Here's some of the propaganda from the website:
The last, but by no means the least, important feature of our sleeping bag is the zipper. We use a #10 YKK molded tooth zipper. If your zipper fails to work when you are out in the field, it is irrelevant how good the rest of your sleeping bag is. I have been using the YKK #10 tooth zipper for 20 years, and I have yet to have a bag returned due to zipper failure. We also manufacture snowsuits and parkas used throughout the state of Alaska. The only zipper I will use for these garments is the #10 because it proved to work at -100 degrees F.