Hi Bob,
DIY will always be "king of the (bass) hill"..
I used a 70" tall, 30" diameter sonotube in my HT room back in the 1990s. Now, it is in our main shop floor at the SVS factory. It actually fills the (approx) 100,000 cu-ft fairly well.
We still help with DIY designs at least once a week (running sims on leap, making basic design suggestions, stuff like that). I've seen enough of your posts to know you know what you are doing though.With a long throw 15 in a large PRed enclosure...no surprise you outgunned the PCU..
We have to worry about stuff like "ship-ability" and we have to put everything to long and sometimes costly safety checks( including CE certification for most products now). DIYers are lucky...they can make them as large as needed and don't have to worry about a little sticker on the amp..
Tom V.
SVS