I need some help on HOW big to make the enclosure for 4 12" P1's. I'm building the box next week and post pics as I go along. But first, I need on how big to make it. Right now I have it so it's 15" tall, 36"X36" wide. There will be 2-3"s in between each sub. So tell me if the enclosure I made is good or not. Thanks.