How many extra layers & type?
On the last night of my Olympic trip, with temps in the very low 40s, I decided to leave my bag in it's sack, inside the hammock. I slept in my light weight long johns and Bozeman Mountain Works Cocoon medium thickness 14 oz hooded jacket and 8 oz pants. (Polarguard delta). With a SuperShelter on the bottom. It was just almost, but not, quite enough. I went to sleep in just the longjohns about 10pm, and was actually a bit hot. I woke up having to pee and cold on top about midnight. I put the jacket and pants on and was fine untill I got woke up at 7am by the noise of friends stirring about. I noticed I was just a tad cold on top, but it was time to get up anyway. Also, every body else ( including tenters) complained that it seemed extra cold that night.

So I was good for at least 6 or 7 hours as the low got down to almost 40*, with no bag. I' sure this would be fine for me to at least 50* with full comfort for 8 hours plus, and the addition of more clothes or a light bag would get me a lot lower.