Battery weight help
 

I'm building a little ultimate 40S over the winter and it is coming out on the heavy side. I've used NIMH for my smaller apps and Lithium Ions on my 50cc airplanes, however, weight has never really been an issue until this project and I have never weighed them.
Question (more like confirmation): Comparing a 2000-2200 mah NIMH to a comparable lithium ion. It looks like there is almost a 3 ounce weight saving with a 2S/2200 lithium. 6.0V only. 4 or 5 flights fully charged would be plenty of capacity. I'm guessing the little regulator is less than an ounce. Does anyone have experience with a liithium that is light for weight issues? I'm looking for a good brand that is light.
thanks