Hello I am hoping someone could give me an easy answer. I have sundown Audio ZV4 v1 12" And a 2.5 cu foot fiberglass box and need to put a port in. I it says i need a 40 sq inch. port tuned to 32 hz. I know a slotted port might be easier for some but the way I made my fiberglass box there isn't an easy way to put a slotted port bordering two walls. I was hoping I could use a round port with pvc pipe. What Size pipe would I need to use? and How long would the pipe need to be? Hopefully this is enough info for you and hopefully you can give me a simple use X inch wide pipe and cut it to be X inches long and ill be all good.