The bass is always buggered somewhere. Oftentimes it's more even throughout the room when there's only one sub (or they are together) ('cause there's less comb filtering - no power alley).
I'd try putting the bass rig right behind the single sub, shooting cross stage. This should minimize comb filtering between the bass can and the bass in the PA.
That is what i did min my earlier post and it was terrible. Like a giant marshmellow of lows.