You may need a second pad to get down to temps as low as you're looking to get. Will mostly depend on you. If you are dead set on pads, then certainly look at double layer hammocks. As far as side sleeping goes, I sleep on my side in a gathered end hammock just fine, but not everyone can.
When thinking about quilts verses sleeping bags a quilt set the quilts are going to add about 20-30% more bulk and 20-30% more weight. But you're also lossing the wieght and bulk of the pad so it tends to balance out. The reasons most people prefer an UQ are (1) more comfortable and (2) easier to stay on top of. The main problem with pads is that in a hammock a standard width pad it simply is not wide enough. You will at some point roll off of it and become near instantly chilled.