Macktoon

Looking at Possibly Doing 2 18" SSD's in the Trunk of a Lincoln Town Car (1996)..On a Massive p1500.1,,, I was just wondering on overall efficiency on the ssd's.. ive yet to play around much with 18's and i figured i could fit a good 12+ cu ft back there.. Im thinking possibly subs up vent back but was wondering everyones input on overall sub/port placement on that specific vehicle