I'm about to buy another Eiger (Ultra X). It's going to be a gift. The person who will receive it will be well educated about how to use it and I'll do whatever I can to make sure they use it safely. That person is a reasonable one, so I expect no problems. But nevertheless thinking that it's thermally unstable and when left unattended it could enter thermal runaway makes me uncomfortable. How about adding a (big, to make sure that losses are negligible) thermistor-controlled FET to shut it down before it gets out of control?