Here is what I would do if I was considering your options:
How tall are you? The full length nightlite is 76" which is 6'4". At a max weight of 12.4oz/76=~.16oz/inch of weight. I'm 5'10", so I'd trim the nightlite 6"+ about 10" for my head. (I sleep with my head off my pad as it's on some sort of pillow (shoes, clothes, whatever)
So, for me, 76-16=60"x.16=~9.6oz of pad, and 60" is plenty to form a cylinder for a frame. I'd have the simplicity of 1 pad vs 2 at about the same weight as the torso-length pad and 3/8" thinlight. If you need more padding under your heels or torso, use your pack.