Personally, I think they should just abandon the use of single tanks in overhead training.
That seems to be GUE's philosophy, as you probably know. GUE offers no equivalent to a cavern course. They don't let you in an overhead until you have a Fundies tech pass, which requires serious proficiency--in the full gear configuration. I've heard it said that the reasoning behind it is that "A cavern can quickly turn into a cave." Case in point is the OP's report in this thread. GUE's logic is appealing. The long road to a Cave 1 cert may not be so appealing.