OK, the 85L ported shiva on Adire's website calls for a 3" flared port cut to 8 3/8 inches. I just got a 4" port by mistake here (sorry Brian, not trying to call you out, just wanted people to know why I didn't just get the 3" one to begin with. I'm cool with our deal 100%). Due to the flared ends I can't simply calculate what length I need to trim the 4" port to, to achieve the same tune of 20hz. I am totally lspcad illiterate. Anyone?