In addition to enclosure resonant frequency (fb), there are also dimensional resonance's to consider.
These resonances occur when the dimension is equal to half a wavelength of the sound, and this could cause coloration of the reproduced sound at the corresponding frequencies. Should this happen, there would be a very pronounced peak at the corresponding frequency.
This can be avoided by ensuring none of the internal cone-to-baffle dimensions are the same.
Height, width and depth of the enclosure should all be different and the drive unit positioned off centre in the vertical plane. This means that if cancellation does occur at certain frequencies, they will all be at different frequencies and the overall result will not be noticeable.