OK, since it's the weekend and my geekdom manifested itself in a focus on numbers, I just performed an essentially useless task.
Just for kicks I took all the extensions off my P3 Ti and threw on the Kabuki Ti. This thing is very cool! Other than not liking dual battery mods very much due to their size, I've never been particularly sensitive to a mod's weight. Regardless, I really like this flyweight setup.
So I checked some mods on my kitchen scale. The juice levels were roughly half full but I didn't try to standardize them at all.
P3 Ti, 350 battery with Kabuki Ti: 4.4 oz
2.5 GMZ, 490 battery with stainless Kabuki: 7.5 oz
P3, 18650, std Kabuki: 8.6 oz
Radius, std Kabuki: 9.3 oz
SX Mini ML class, std Kabuki: 11.4 oz
Istick 20w, Nautilus Mini: 4.7 oz