With your height I'd suggest A Western Mountaineering Megalite 30 F. bag (in long) due to its greater girth. I'm 5' 10" and have one. I like it B/C I can wear my down "sweater" jacket inside on cold nights W/O compressing the bag's down. This is true "double duty" use for a down jacket.

For my legs & torso (and to protect the jacket and bag from body oils) I have lightweight to medium weight long underwear, depending on the lowest expected temps. And don't forget fleece gloves for 15 F. mornings. (Yes, it can happen in High Sierra valleys even in August.)

Also the Megalite's width makes for a good quilt when fully unzipped on hot nights. Just hook the foot over your full length mattress and use as a quilt. Feels as comfortable as home.