I think it would recover better. But once the DHG goes through the Die-Off transition stage it will start growing faster emersed.
So it depends on if you want to risk waiting or just flood it now and just wait a little longer for the DHG to grow.
I'm sure the DHG could survive through the emersed state.
Argh choices, choices. I think I will flood it, just because the DHG has really not shown any signs of life after 3 weeks. It still has enough of the original green to suggest that it still is locked into submersed mode. And if it fails entirely...well I'll do something else! Thanks so much for the help!