I cut my full length GG Nightlightdown to about my knees and it easily folds into 1/3's for use as a frame sheet in my ULA Ohm. Rolling it up took up way too much volume inside my pack, but that's with my gear so I'm sure it varies.
I think the GG Nightlight folds quite fine without needing to score the pad, there is a certain amount of memory to the foam. Personally, I definitely wouldn't recommend scoring the pad at home, I tried very lightly and precisely scoring a small section of my full length Nightlight with a very sharp razor and found that after folding over and over on the scored line that the incision grew and eventually ripped through in about 30 seconds. I wasn't confident at all a home scored job on a Nightlight pad would hold up very long in the field.
Suluk46 offers a great variety of pads that can be cut down to specific sizes. I purchased a pad from him and was very pleased with the pad and his service:
Also, don't forget Nunatak! They're selling their version of the Mt. Washington style pad called the "Lunapad". They currently have full length 2nds w/ cosmetic blemishes on sale for only $25. They're made of Evazote, basically the same material as the GG pads, but in-stock and cheaper:
Nunatak Lunapad (scroll down to Sleeping Bags section for clearance)