At subwoofer frequencies (~40-100 Hz), I don't believe you need to port the cubby lids, only the bottom(s). At least I didn't (but I'm no audiophile; just as in Art, I don't know much, but I know what I like). Free air subwoofer on the bottom of the cubby area may be what you want as in this posters question
need free air sub

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)