That sounds good, but I'd definitely run it vented. A Delta 12LF in a 2.0ft3 bass-reflex box tuned to 40Hz has f3 of 48Hz and f10 of 33Hz and the response curve is nice and flat.You can make it slightly overdamped if the room conditions merit it by tuning slightly lower, which gives rolloff slope similar to that of a sealed box. For example, tuning to 38Hz gives f3 of 50Hz and f10 of 32Hz, tuning to 35Hz gives f3 of 55Hz and f10 of 31Hz and tuning to 30Hz gives f3 of 60Hz and f10 of 30Hz.
A Delta 12LF in a 2.0ft3 sealed cabinet is OK too, but f3 is 80Hz and f10 is 40Hz.