Port Placement

[TribeamConnek 0]

I have a 1989 Dodge B250 Van. I removed the backseats and built a platform to hold a setup I am getting ready to build. I will not be building a wall. The subs were going to be facing the back of the van and my plan was to have the port on the back of the box. Do you think that would work properly or should I move it to the front. The speaker box will more than likely 21-24cubes and tuned around 32hz. It is supposed to be for 4 18's or 6 15's. I am leaning towards the 15's.