Emily, I'm pondering your focus on weight. At what PSI are you running your tires? MTBs get better traction if you run your tires as low as possible. Since you are light, you should be able to go pretty low on a FS bike. A good way to determine this is to lower the pressure until you start to get pinch flats. Add back a few pounds of air and that's the pressure you want.

I'm 134-140 depending on my consumption of naughty things and run my tires about 32 psi. This is on all my MTBs and we have lots of nice sharp lava rocks around here.