I think that 3 times the charm....
First liner -- silnylon with 8 pockets filled with down. Toasty warm on a cold 28-30 degree night. Bulky even when squished down. Weighed 1 pound. (I still used windshield reflective pad inside hammock.)
Second liner -- silnylon with 8 empty pockets. Fill pockets with partially inflated plastic produce bags. Toasty was in low 30's. Time consuming to inflate 8 bags... well only like 5-10 minutes but I'm a lazy cuss. Weighted 1/2 an ounce, plus weight of plastic bags. (I still used windshield reflective pad inside hammock.)
Third liner -- 1 large crib pad (fleece covered rubber pad). Added 12 inches of sil to each end and gathered ends together. Added ties. Haven't been able to try this is COLD weather but I know that the pad will NOT LET cold air through. You can't even force your breath through the pad. If it were super cold you could always put bags between the pad and the hammock but do not feel that this is necessary. It can be used inside or outside the hammock, as well as in shelters. It is washable. It folds down to a nice small package and weighes 9 ounces. (With this I have also OMITTED the windshield reflective pad.)