So, back to that starter I started 3 weeks ago...
For the next few days I continued to put it in the oven over night with the light on. But on the 4th day it started looking flat. It would be nice and bubbly after adding the 1/4 flour and 1/4 of water, but by morning all was still. And when stirred it was very soupy. So for a couple of days I skipped the water and only added flour.
That seemed to perk it up a bit again, but it would be flat by morning. I decided it was because I was not feeding it enough. And I stopped putting it in the oven, letting it get a bit cool at night (around 60 degrees).
When I got to two cups of starter I did a loaf of bread.
I really thought it would take longer than 30 minutes for the loaf to double. It did not. And it continued to rise as I heated the oven.
And: not too sour. Could be for a couple of reasons. Maybe my starter is too young. Over time it may get more sour. Or maybe the natural yeast in Hawaii just won't make all that sour of a loaf. Either way, the starter now has a home in my fridge. I'll give it a few more loaves before I decide how worthy it is.