Lightweight mice are amazing, never really realised until I got the first proper lightweight mouse last year, the TurtleBeach Burst II Air, 42g, it was a rabbit hole from there onwards looking and searching etc. The Pulsar X2 CrazyLight is my current mouse at 35 grams, feels awesome just finger flicking about with absolute precision and very little inertia.
I think to get any lighter than this you end up with a mouse with loads of front facing holes or rigidity issues, so I think 35g on the X2XL is about the best compromise on traditional shape and shell, with rigidity but still being super light.