So due to a variety of reasons, I stuck with my original order of 2 Xmass' (Xmasi?).
I tried to get some Sonotube from Home Depot last night, but their book didn't list anything larger than 12", so they checked their suppliers site which stated sizes up to 24", at the perfect 12' length. I'll call the supplier on Monday to see if they can get the 24" size and ship it to my local HD.
That would put me at 2x 24" diameter columns, at roughly 18.5cf each after everything except the port - which will very likely be an 8" diamter unit around 4.5 feet long tuning into the low to mid teens.