Unwanted advice served up fresh. Figure out a way to cut that baffle out. Put cleats just behind where it use to be in order to be able to fasten a new baffle. That will also allow access for additional bracing. I wouldn't be so bent on a 15" sealed design. For the money I think you get a lot more sub if you give up the lowest frequency and the highest SPL. A port buys a lot of LF capability and if you're giving up the highest SPL, you can let your port size determine max SPL and power requirements.
It sounds backwards but that will get you a working sub that covers 80% of you listener needs for 20% of the cost not to mention avoiding the work of a slot port. I like the cabinets! I was just talking to YAA about finishes being the worst. Those cabinets have grills! Dude, you're half way there!
