Well I'm new to DIY subs. I've had a RLP18 just sitting around for awhile, and decided to do something with it. Its almost 100% home theater, i'm still learning all the programs like winisd and have been playing around with the enclosure calculator. So I decide to make something about 13-13.5 FT3. Thinking about down firing with a 24x24x60 enclosure 1.5" mdf, I want it ported at the top so what kind of port length and diameter should I be looking at, when playing around with the calculator I put a 17" long and 8" diameter port, would that work, not looking for SPL more hard hitting low bass for movies. Going with the ED lt1300 amp. Going to use 3 0.75" 21x21in bracing with 8" holes. Is there anything I'm missing or not doing right or something I should change? Just making sure, I don't want to screw anything up, so if anyone has any options that would be great. Thanks. Oh current sub is a SVS 25-31 PCi, this shoud be a major upgrade right?