? on Kicker 12L5s

I have 2 12" L5's i want to put under the backseat of my 2004 ex cab Silverado. I have designed the box and it works out to be about 1.22cuft of air space per sub, but i dont know if the displacement of the sub will off set that or not, so the question is based on the info that came with the subs, it says that they need .88cuft at the min, but it says that the displacement is already worked in. thats where im confused. the displacementfr the 12"L5 is 131.1CuIn. Any help would be great thanks.

Jimmy

i am trying not to have the box hanging out from under the seat, so i only have about 8" of height and 13" of depth the width is 58" and it is going iver a hump. I can use polly fill to get an extra bit of air space if needed, but i just looked at the website again, and the min box size is even given 13 x 13, 13 x 11.5, 11.5 x 11.5, that only comes out to .88cuin of air and thats not taking in the sub size. so i guess that i should be fine.