I´m a bit confused by tuning the ports. My cab net volume (vb) is about 2.92 cu.ft (82.7 l), I have the kappalite 3015 speaker and two 4.331 in (110 mm) diameter ports. I´m useng winISD beta and bass box pro 6 as well. If I have port lenght 4.935 in (125 mm), then bass box pro says that my tuning frequency (fb) is 54 Hz, winISD says 57.5 Hz. Which should I trust? Anyway which tuning is the best if I`m after punchy ampegish (but clearer, less boomy) rock bass tone?