Does the XT live has a dual mode for using two tones at the same time? Or a loop function? If not you will only be able to use the xtl and dl4 in chain.
You might try to run them parallel by using a signal splitter box (A/B box). So you could send one guitar signal (A) into your xtl and the other one (B) to the dl4.
Check out this site <http://www.amnesta.net/edge_delay/#songlist> if you haven't already done that. It gives you the exact delay settings for most U2 songs from Boy to the Bomb.
I've heard many from other gear sites state that a lot of the info on Amnesta is unreliable at best.