Although I have preferred shimano since the days of hating grip shift I found GX circa 2011 held up well. But NX and GX from 2018 were pure crap. I find the reasoning that the jump to 52t is okay because it's not that much worse than the (already poor) jump to 50t to be pretty weak. Appreciate the article, more reason to move on to XT 12 speed once my 11 wears out.
Used to run a 888 set to 170 mm on my '05 stinky with 6" (so ~150mm?) In the rear. That was a sweet overfork for hucking until the frame failed at the bottom of the seat tube where it was welded to a plate above the bottom bracket.
I have a 2018 mega trail, it has 2 rear shock mounting positions to switch travel between 165 and 150 mm along with a slight Geo change.
I got a second, shorter stroke shock with same eye to eye so Geo is the same but travel is reduced to 145 or 135 mm. This is basically the same as a shred Dogg but with my same longer travel fork. Although I air up the fork so effective travel matches the reduced rear.
I think the 29" smash could do the same thing but recommend just contacting guerrilla gravity they are super helpful folks.