This is starting to remind me of a recent thread that I posted in:
Link
You guys got the same set-up (X-REAS with DS Spacers) and apparently the same issue (Loose rear end).
Unfortunately the OP has not replied as to whether he was able to get this resolved yet, but reading through it might give you some ideas.
I'll tell you now, I've got a DS lift and it's been great to me, but I do not have an X-REAS suspension.
Good luck bud!
Thanks for the link, but most those guys are pointing at a faulty install. Which didn't happen, as I was there throughout the whole thing, and not a single drop leaked.