I just got a WBBB 1.1 dbl, and am using my Big Agnes sleeping bag with it. Because both the sleeping bag and the hammock have "sleeves," this is what I have been doing the few times I've hung out this winter, with temperatures down in the 20's.
I put my 20 inch wide Big Agnes Insulated Air Core pad in the sleeve of the sleeping bag. This in itself is a lot of insulation, but more is needed for winter hanging - both under the Air Core pad and along the edges of the sleeping bag, where the insulation gets compressed by the hammock.
So I took a couple of $5.00 Walmart blue 1/2 inch CCF pads and a $2.00 mylar Emergency Space Blanket and fabricated something that looks like a Speer Pad Extender. I cut one pad into thirds, and then connected these back together with pieces of para-cord. I put a drop of Superglue on each knot, so that it wouldn't come undone.
Next, and cut four 10 x 20 pieces and two 5 x 20 pieces out of the 2nd CCF pad, and attached these "wings" in pairs to each of the three sections with para-cord.
I also spray glued pieces of Emergency blanket onto what would be the top side of the pieces of CCF pad, and duck-taped the edges for added strength and durability.
The result: a pad that I can put in the sleeve of the WBBB, and which contours to the shape of the hammock perfectly. The BA Insulated Air Core pad and the sleeping bag nestle right into it, and the sides of the sleeping bag have an insulated wall around them.
Note: the "wings" are shorter than each of the three inner sections. This works perfectly, as the wings come together when the pad is in the hammock, due to the curved shape that the center three sections assume.
When I remove the CCF pad from the hammock, I can fold the "wings" inward,
and then fold the three inner sections together, making a light-weight package about 20 x 24 x 3 inches.
I can carry this on the back of my motorcycle without any concern for it getting wet, as it's all CCF.It also is flexible enough to curve around the outside of my backpack when hiking instead of motorcycle camping.
Total weight of the CCF pad: my guess is: under a pound.
The real low temperature test of this arrangement will be at the Colorado Winter Hang in the end of February, up above 9,000 ft. in the Rockies. It should be pretty cold at that altitude.
I'm thinking and hoping that in the summer, here in the Rockies, the inflated Insulated Air Core pad might be enough bottom insulation all by itself. - I will find out, I am sure!