porting through rear deck

alright so i built a box for my zcon inside my trunk cause it was to big to be able to slide in , its 4.5 cf tuned to around 31 with port and sub facing the trunk,, i was wanting to know if there would be any down falls to closing the slot port and putting in one or 2 big aero ports toward the back of the top of the box and go up through the rear deck where the 6x9 hole is. im thinking about doing this because ALOT of air is getting out of my trunk and not making it up to the cabin,, and where my back seats fold down its not big enough to have sub and port facing forward and really dont want to have to cut the box out of my trunk, and i would really like to be able to change the tuning for competitions and stuff