My current arrangement involves two pads: the sleeping pad is a MultiMat Adventure Compact XS, cut down to a hair above torso size; the second pad is a sit-mat, a thin piece of foam given away free with a hiking magazine many years ago.
For breaks, and also to kneel on when getting under a low tarp in muddy conditions, I like having the sit-mat handy in a side rucksack pocket, so I almost always carry it anyway. At night it goes under my feet; the gap between it and the torso mat is just taken care of with the quilt and bivy bag, since that part of my legs tends not to touch the ground when lying down. I might put my (frameless) pack under there if it's a bit nippy, but in wet conditions the pack stays away from my sleeping gear, since I never use pack covers.
Weight for this set-up is 62g for the MultiMat and 12g for the sit-mat, a total of 74g (2.6oz) which I think is quite good given the versatility of the two pieces.