The plastic foam pipe insulation tubes sure seemed like a good idea, but the leaves on both Amorphophalluses died anyway, before the A. bulbifer could grow a replacement bulb. Which is the bad news.
The good news is that the A. bulbifer, at least, is willing to grow a replacement leaf in the same season, so I haven't lost the plant entirely after all.
The A. konjac hasn't done anything yet to indicate that it's thinking about replacing the leaf that died. I can see the top of the original tuber when I look down into the hole left by the leaf, and it's at least not dead. Which is something to cling to for the moment, I guess.
One of the A. konjac offsets also got a wind-bent leaf, which subsequently came off, but two remain. At least in theory, they should be able to hold on until the fall, and then I will have more than one konjac. Which I will put outside in a timely fashion next year even if it means I have to move them in and out a lot, because that's how excited I will be about having more than one konjac.