Here is a couple videos I thought were interesting on shocks and springs.
This one goes over the different types of rear suspensions, solid swing arms and IRS systems. Doesnt talk about the xx but good info none the less.
If you notice in the vid above he talks about how the conventional swing-arm on solid axles effects the weight to the front and ride/power to the front and how the IRS is different. This makes me question what the best setup for our xx IRS could be. Is it different to setup then a typical strait axle setup and exactly what is needed to setup different. I am going to take my xx out today and mess with the stock shocks and preload to see what I can figure out, just for my own understanding. I know preload adjust ride height but I know typically you want the front to be a little higher then the rear sag. I am wondering if on these IRS if that amount is the same or if it needs to be increased/decreased to get better performance, of course I know this is all relative to rider style and weight but just trying to get a good baseline for others that may want to adjust theirs. Please if you have nay input the knowledge is appreciated.