If you build it with internal dimensions of 16" cubed then you are almost there.
That makes 2.37 cubic feet. Optimal is 2.4. This will have little change.
If the 16" cubed is external and the box is 3/4" thick then that will leave only 1.764 cubic feet.
It will knock the -3db down point up to 24Hz from 20Hz.
But then you will need a brace or two plus the woofer and PR take up some space too. Your likely looking more at a -3db of 25 to 26Hz.