Okay then. Imagine you bought yourself an underquilt...ok? And so now you have to hang it under your hammock, right? So you hang it by the suspension line given to you by whatever company you bought it from.
But it's suspended too tightly, so when you lie down in your hammock, your underquilt's loft is compressed and you still feel cold... now, when you loosen the suspension a bit, it will force the underquilt to hang a little looser under your hammock and it isn't so compressed. Now when you lie down the underquilt is not AS compressed, but you still feel cold under your (just for instance, your LEFT) hip when you sleep on your side... so you then hang the underquilt even a bit LOOSER and now you are nice and toasty warm in your hammock and you have no pads in your hammock that keep sliding around during the night getting in your way, and you sleep for 8 hours straight and feel great the next day.
It helps to have someone OUTSIDE the hammock adjust the underquilt while you are inside, to get the best fit.