Generally you want the port to fire rear within a few inches (usually 6” or less, a lot of factors to that) of the hatch, because that creates a pressure zone behind the box that causes more pressure in the box itself, which tends to make your entire bass system play louder across a wider bandwidth. There’s usually a golden zone, especially with SUV’s or large cabin vehicles. The air loses energy quickly when firing the port forwards, like the energy dissipates too quickly, and the inside of the box just can’t build up the same amount of pressure vs firing rear. What you want to do, in general, is slowly increase the cross sectional area from the port opening into the cabin, instead of have the port just dump out into the middle of the vehicle into a huge open space.