John Muir maintained that you'd never be cold as long as you had enough wool blankets. I think he's right. I've laid on them inside the hammock before. I don't think you'd have much luck rigging them as an underquilt, though... they'd leave too much of an air gap. Just like anything else used inside the hammock, they shift around a lot. CCF always works well; it just happens to be light.
.. truly to enjoy bodily warmth, some small part of you must be cold, for there is no quality in this world that is not what it is merely by contrast. Nothing exists in itself. If you flatter yourself that you are all over comfortable, and have been so a long time, then you cannot be said to be comfortable any more. - Herman Melville