Some quick googling just now suggests that the XLS isn't supposed to run with 2ohms if it's in bridged mode.
From the manual:
View attachment 97274
Even just from familiarity with the amp, as much as it sounds like a whole ton of power, that "1100 watts" runs out pretty quickly even just with one cab. Not sure I'd want to push it much more than that.
If running two cabs, why not use it in stereo with the built-in crossover? That's probably the ideal setup anyway, given the difference in cabs.