I own and used for several years a Macpac Neve, one of the original “top bags” it had a sleeve for the sleeping mat and was a vast improvement on other sleeping bags in my view, its disadvantage was its weight.
Along came the Sleeplight a top bag made by Nunatak for GG. I used this sleeping bag on several trips and with temperatures dipping into the 20’s and I always felt comfortable. The benefit of such a sleeping bag IMHO is that it emulates the properties of a quilt whilst having a single layer of silnylon underneath thereby eliminating drafts.
When using the bag I was initially worried about staying on the “no down section” it was never a problem. As well the hood of the bag was easily cinched up and enabled me to keep my head warm without the need for a hat.
At 18 oz I find it to be my preferred sleeping bag.