As I recollect, Jeff, (I may be wrong) on the previous thread about buying this PA, the bass amp had its own DI out so rendering a separate DI box unnecesary. You are of course right that that leaves the bass amp pretty much as a dedicated stage monitor. To "hear" the bass rather than feel it, add high-mid and even some top. If the bass is "robbing" the other instruments in the mix, you may have to turn up the stage amp and down the bass guitar in the PA.

By and large do NOT put bass or kick drum (where present) in the monitor mix. All you get is blown monitor speakers.