Methinks the evaporative cooling set-up did it's job just fine! Between 11:00 to 1:20 the inside temperature creeped from 85 F to 90 F and has held steady since then (writing this at 3:30). I'm calling this a not-too-shabby success, since the outdoor temperature climbed from 91 to 97 in the same amount of time.
So I didn't quite reach the wet-bulb temperature of 84, but here I am writing this entry - a bit balmy, but if it were 97 indoors I'd probably have passed out before finishing this paragraph :)
Lots of thanks to Make: Magazine for featuring this project!