Long story short, I built something similar well over a decade ago and it failed miserably. ... but it only took one baffle to turn it into a simple ported enclosure that hit hard....... allong my travels, I found that the general principal will work, but it takes a whole lot of calculating to get it to work, or sheer dumb luck. .... not something I suggest taking on just for fitment issues. There are other options. I'm a fan of glassed into the rear sides, but, if you already fit 2 rear-firing, then perhaps, look at fitting the orts above or below...... or even bandpass, ported through the rear deck.