I just finished making my own pair of insulated mittens! I used:
2.5 oz climashield
1.1 oz uncoated ripstop for inner shell and back-of-hand's outer shell (green fabric)
Heavier (more durable) ripstop from JoAnns for the palm's outer shell (gray fabric)
Finished, the pair came out to 1.55 oz. I used the size "Large" mitten pattern and they fit well over my hands wearing a light pair of size medium gloves; I did cut 2 inches off the length of the pattern. Before I sewed it in, the Climashield for both mittens weighed a total of 0.7oz, so you could double the insulation for very little weight gain.
Thanks for posting how to make these!