Hi, John- I didn't use an additional pad; I just took the Neo on a 13-day trip. I put my 16" square sitpad under my back a couple nights, and spent a few of the coldest nights in a VBL fashioned from an emergency blanket.
The comfort of the Neo is great, but I personally don't see it as anything more than a summer pad. If you combined a shorty ridgerest it would add 9 ounces, and a thinlite would add another couple ounces. Weight for the 3 pads would be about the same as a Women's Prolite Plus (~25oz), but I think the effective warmth of the P.Plus (R-4.5)would be greater. Again, a personal preference, but I really don't want to mess around w/carrying 2 or 3 pads. In terms of comparison, the Exped Downmat 7 short weighs 22 ounces and is roughly 30% warmer. Full-size weighs 31 ounces, R-5.9.
Again, realizing that much of this can be personal... I think the Neo is a remarkably comfortable, light, compact summer pad. I suppose that if you carried another pad for warmth and the Neo more for comfort you'd have a workable system in 3-season use. The question to me is whether or not there's a more effective system. I guess the prime benefit w/the Neo/CCF rig is that you can ditch the weight of the CCF for summer trips...