18" Bl box help

Alright so i'm going to buy an 18" fi bl before summer, but i want the plans for the setup before i buy. My box is 31"H 35"W and only 17"H, and will have a 3" port going along the 31"H, tuned to ~30hz. The sub will be on the same side of the box as the port, is that a problem? The only thing i could think of is that, im taking up 2 seats in my quad cab dodge ram for this, and because of the seat it will be set at an angle. Will the sub perform right, and what should i do, if anything, to my box since it will have the strain of an 18" sub on it. The only way i could get around this would be if i put it in the bottom corner opposite the port.. how does where i put the sub on the box affect sound? I know theres a lot to answer, but i want this to be right.. thanks everyond who answers.

Also, i was going to use 3/4" MDF if that helps.