I bought a white version of the Logitech G305 and on top of that, got some AAA Lithium batteries along with AAA-to-AA converterers today. That 10g of weight delta makes a ton of difference and I can feel it so prominently, not sure what took me so long to get this simple mod done...

Some weight comparisons of my current mice:

Logitech G502 w/ 3x Weights (towards the back) = 139g

Logitech G502 bare = 116g

Logitech G305 w/ AA Alkaline = 97g

Logitech G305 w/ AAA Lithium = 86g

Logitech G305 w/ AAA Lithium + No back cover = 78g

So I've essentially gone from a 139g to an 86g mouse, and that's awesome.