It already has a double front baffle (1.5"), you can change the outer front baffle if you would like but I am unsure as to how the speaker would sound if the drivers are not on the same plane.
The interior dimensions are important, the outer ones not so much. If you want to add more to the outside of the speaker it shouldn't be problematic.
note; all hardwood cabinets tend to have some 'bad' resonance.