Most times when I run a sim on a subwoofer, I always seem to specify round ports, even though there are options for rectangular ones. Is there any compelling reason to make a port round? Or do rectangular ports serve as well? On a related topic, I often notice that some people prefer dual flared ports (on round ones, of course). What effect does the flare have on the port? Can you get away with a slightly small port by flaring it? Or are non-flared ports just as effective, but perhaps less aesthetic?