Untitled from alexander belevskiy on Vimeo.
Way too good.
Untitled from alexander belevskiy on Vimeo.
A SRAM PG-950 (used), 11-34t, weighing in at a pound clean.
160g with a steel lockring, 6 gears and an 11-23t stack. Competitive against road cassettes in both spread and weight. I rode it for a bit, and found I wasn't using the easiest gear, so I proceeded to V1.75 -
110g with a steel lockring, presumably around 103g with an aluminum item. Very competitive weight. 11-20 spread, 5 gears at this point. But it shifted like utter crap, spitting my chain around at will. So I bought another cassette, a Shimano and a road unit at that, because presumably this would improve the shift quality. Cassette V2.0, 213g with steel lockring. 12-24t spread or something like that. 
I opted to keep 6 gears as the stack would be harder - 12-17t. 116g with a steel lockring. Not satisfied yet, but hopefully it will shift well. My ultimate plan would be a new chain and a reduced Shimano 11-28 cassette with an aluminum lockring.