I think I found the problem (I wish the Atlanta Falcons could find their problem).
I noticed earlier that the rear carb choke arm wasn't moving as far as the forward arm. So, the first thing I wanted to do was look at that. Loosening the bolts and twisting just a little seemed to resolve that problem, so I took the plane back outside... it's running on all 4!
I took a short video, nothing really to see. It's idling a little rough, seems very rich. I'll take a closer look at that some day soon, but I really just wanted to hear it running this weekend. I'm headed out of the country for a few days, so maybe I'll spend some more time with it towards the end of the week.