I modeled up the enclosure in BBP6 using the metered results from the meet which you did a 142.6 @ 46hz.
I monkeyed around with design using the enclosure you have for the baseline to gauge the design results.
If the enclosure were 3.25 cu.ft.@ 36hz with a Fs of 34hz doesn't really do much in terms of dB gain for the output. For what the graph plots show, the enclosure is more max flat than anything.
However, an enclosure at 4.0 cu.ft. @ 40hz with a Fs of 35hz with have a dB gain around 2 - 2.5 around 44-48hz range.
For this enclosure SQ is going to suffer alittle bit but given the Ts spec's of the subwoofer with this enclosure being larger in volume will still reinforce low end bass response but the higher port tune will give you more output for the dB increase and give ya that 143 your looking for.
Thanks phil i appreciate it. im debating on if i want to build a new box or wait, because im thinking about getting another hdc315 and another zx1000.1.