Y9u have to realize the enclosure recommendations are not going to necessarily be perfect for every application. They are simply playing the numbers. This enclosure is going to be best suited for the vast majority of users, unfortunately, you don't apply. You're tuning an enclosure too low for what you want it to do. There are many factors that come into play. You could have a cancellation issue, a phase issue, impedance rise, etc. . . I get what you're saying, but you can't always expect it to be that simple.