15'' Punisher Design

Lockdown seems to me the perfect time to redesign the sub section of my rig and come up with something completely new. I currently run a punisher rig and for the most part im pleased with it. However i recently purchased a pair of Void Stasy 8s for kickbass and now i find myself really wanting a sub that hits slightly lower than a standard 12'' punisher. I've toyed around with various design briefs and after finding the Ciare 15 SW i've decided i really want to make a box for it designed to hit 30hz as flat as possible whilst  still retaining alot of the "SPL over low-end extenstion " and "fast moving small surface area over slow moving large surface area" approach to the original Punisher design. I am aware that there is a plan for a 15'' box that would fit this driver but to my knowledge it just a scaled up 12'' plan and what im seeking in asking this forum is advice, parameters and tips to redesign the horn as i believe simply just making it bigger is not the best approach to getting extra low end extenion from a punisher sounding & style box. It will be my first attempt at proper speaker design so am looking for any and alll pointers that will help me along the way and am re-familiarising myself with the Dinsdale Horns Guide alongisde writing this.

Thanks in advance

The Punisher folding is clever, but a PITA to assemble. Without CNC cut parts - V diff. (I've built 8 that way...)

If you're into complicated woodwork, why not build the "I Can't Believe It's Not A Martin 215 mk 3"? The plans just came up on here the other day - and it will satisfy your goal of fast, efficient bass.