Something interesting you could try...
If you blocked of the higher tuned port it would give you a sealed section (1.3 ft^3) resonance of about 32hz. Given that your other vented section is right around that tuning and about twice the size, it would give you a reaaaally low tuned 2:1 4th order. That could be fun but because of the low tuning you'd waste a lot of the gain you get from a 4th. I'd still try it out though since it would be really easy to do.
The three chambered enclosure you posted wouldn't provide much, if any, gain over a regular vented enclosure unless it was absolutely massive. I have no way to model it, but I'm guessing it would provide really good cone control due to the multiple Helmholtz systems, but would be really hard to get right.
I should point out that cone control is better
in vented enclosures than sealed enclosures until you get below the tuning frequency. That makes me think that perhaps your low-tuned chamber isn't tuned to the frequency you think it is. For a 2.3 ft^3 enclosure and 6" port it would need to be over 30" long. Is there any particular song of frequency range that bottoms the speaker out?