SuperStockers are notoriously high, but not XHD's , adding 2" to them as they are stiffer is gonna leave You up in the air alright tho'! If You've got stock hangers & shackles,
I'd see if those can be de-arched appropriately, I agree with not using blocks at all if possible. Did You test the set after the re-arch before adding the other upgrades? The
bilstiens are probably more aggressively gas-charged & ain't helping matters, not a lot of weight back there to begin with.