This is going to be an boring answer.
It really depends on the type of bass trap. If it is a resonating bass trap, those are often set up to have a bit of free air behind them. If it is a "damping" bass trap adding to the damping should only help.
what type of traps are these? Are they absorber panels that you'll be placing at the corners?
or are they side wall/ceiling mounted panels?
How thick are the panels?
If these are DIY absorber panels (foam/fiberglass), I'd lean towards having them just be covered
with fabric on both sides, and space them 2-4 inches from the wall if space permits, for increased effectiveness.
Of course this answer may change if its a different type of panel being used.