It being some 6+ months on since getting our "HoverCOUCH"..(cough) up and running, I thought I'd post a quick update:
Surprisingly, I haven't found a need to adjust the air pressure in the inner-tubes. As expected, the pressure does fluctuate slightly with temperature(gas law and all that), but it's no big deal.
I too WAS concerned with durability, but so far, I've been pleasantly surprised. Similar to Trhought's approach, I placed several small wood blocks around the perimeter beneath the HoverCouch to protect the JBL's - "just in case". My racing background affords me a "run it hard til it breaks" mentality. How else to find the limits? Bring on the football team I say!
One unexpected benefit of the innertube suspension, is that the HoverCouch remains anchored "rock solid" to the carpet. If I were setting up a HoverCouch platform on a concrete substrate, I think I'd place a carpet beneath the inner tubes to help protect them from the abrasive concrete, just in case...
It should be said that I'm still very happy with the approach I've taken. I've found that the tubes go on sale from time to time for as little as $7 each. At present, I'm using 6 of them(1 under each JBL & the rest to support the adjacent "L" section of the couch that is "passive". The passive section moves in sympathy with the main "active" section synchonously, to an extent that no discontinuity is appartent other than that the effect is somewhat attenuated.
One of the things I enjoy the most, is the depth and gradient of the tactile experience. It's kinda freaky, as it's a totally unique sensation, foreign to anything I've experienced in the "natural" world. I just watched Avengers "End Game", and appreciated that effect.
My hope is that the Boss(and HoverCouch) will inspire others to further refine, develop and innovate ULF technology to its greatest tactile potential.