18'' solox

i bought an 18" solox kicker subwoofer. and being as stupid as i am i forgot to measure the trunk. the trunk depth is 17 in. but the other dimensions are 4.5ft. and 5 ft.it is a 1969 dodge charger. i figured out the only way it will fit and was wondering if it would work. if it have it a box aiming the sub woofer UP (the sub is 11 2/3 in tall)17- ~11.5=5.5, minus the 1 in. for the box thickness on the bottom (5.5- 1= 4.5) and the max excursion is 0.96 in (4.5- .96= 3.54) would it be ok if there was only around 3.5 in between the sub and the trunk lid (its would be a ported box by the way)? any help, suggestions, input will be greatly appreciated ASAP. Thanks, John

A possibility is to slant the face baffle so that you could free up enough room to mount that sub.  If it would fit that way it would allow more air space to the trunk lid.  But I've seen installs in tighter spaces than that before.  Make sure you allow enough space for 3 or 4 layers of sound damping on that trunk lid.