Wow, interesting discussion! Right now I'm not sure the IAA is going anywhere. His dose has been going up and down slowly between about 5 and 6.5 U for the past several months. One thing that means is that I'm sometimes making smaller adjustments (0.25 U) even though I'm over the 5 U threshold for switching to 0.5 U increments. Seems like when I go up too fast I overshoot and we get lower BG numbers and some rapid dose reductions (the "IAA is breaking!" fakeout), then end up coming back up. So at the moment I think my plan is that if he drops under 50 three times, I'll take a 0.25 U reduction. (Especially right now, when he has really only barely gone under 50 twice.) But if he drops below 40, he'll get a 0.5 U reduction. I might adjust that depending on how long he sustains the drop. Skips and BCS are also still in play, of course, depending on the circumstances.
How comfortable I am with low numbers depends on how he gets there. When he's been surfing greens and just dips a little lower, it doesn't bother me that much. It's the swan dives out of the 300s that scare me, and that's the reason we check him so frequently even when he's stuck in the pinks.