Hello, i got a 8.75 cu ft wall in my car. I am running 1 dc audio level 5 18". I got the box made so i can use a removable port. The max dimensions for port are 22"height and 8" wide. Ive only made 1 port for it so far but i think the port area was a bit too small. it was tuned to aboout 33hz. I want to make a port for spl somewhere in the 45hz range. does this sound about right or should i tune it higher? I was going to use more port area for the spl port. I was thinking of 15" high by 8" wide and 10" deep tunes it to about 44hz. Thats 120 sq in of port and 16.5 sq in per ft....And for the daily port i wanna tune it to about 30hz i think to start with. How does 11x8x25 lenght and that will tune to about 31hz. Any suggestions on anything i should do differently? I know its a lot of trial and error but i want to start in the right direction.