Cubo12 pd12sb30 "extreme" settings ?

Hello,
back on the forum after having built a cubo 12 a few years ago;
As I dont get many occasions to put it to good use nowadays, I thought next time it'll go out, I would try some "extreme" settings to extract the lowest and strongest notes possible to enjoy some dub music !
I always used it from 40 to 90 with 8' tops and good results, and was wandering how much could I reasonably push it to its lowest extreme? (without any damage)
Speaker inside is good old PD12sb30 (still going strong!) and amp is T-amp e1500, which I could use mono bridge if suitable. (2x 850 @8ohm or 1x 2440 bridged on paper)
DSP is T.racks DS2/4 for limiting
Was thinking about:
-add eq boost @ 40hz? or lower?
(what frequency-(ies) and how much could it take?)
-lowering the hpf a bit?
(how low?)
-a combination of both?

What do you think?