still, the general rule is round the biggest ring and add two links, that's pretty much right any bike, unless the chain length changes drastically under compression.
Doesn't always work well with suspension bikes as need to account for chain-growth. I learned the hard way and now remove my shock to cycle through and find the longest point then join it.
x0 is much more accurate than the saint , the only shimano derrailer that is in the x0 level is xtr .
And in the terms of the brakes what matters in dh is not only power but sensiblity and modularity .
Works good for me. Little bit less power then G3, but more modulation. Rode them last year to. Tryed the Ashima Ai, but ended my bike as a vibration dildo for girls when braking.