well, maybe you could all this one the MARYsub... :-)
...where did the "T" go?
the "T" was lost when you castrated it with the LR4 HP
green is with no filter.
black is with LR4 HP
(4 is the order of the filter, which is 6db per, so 24db/oct)
magenta is with a little EQ added back in. alternatively you could use a shelf filter to push the high pass down to around 16hz, but you might feel more comfortable with this one:
Parametric EQ: f=20hz, Q=1.40, gain= +3db
that driver's xmax is around 22mm, Klippel confirmed, so it should have even a little bit more than that as potential. in model, the 1000 amp pushes the driver to just past xmax in your enclosure, suggesting that it should be find with no limiter set. the 1000 watts number isn't really the number. that is a screwball voltage peak figure. the real number is something like 700 watts or so.
btw, if you want to know how to push the high pass filter under 20hz:
How to extend the high pass filter below 20hz in DCX2496
lots of "likes" for you. :-)