I finally tried the meat tenderizing with baking powder. I'd judge it a success.
I used flatiron steak (basically a slice of chuck, very tasty, but tough). I poured the powder over both sides and worked it in with my fingers a bit in a baking dish, put it in the fridge for 5 hours, rinsed it thoroughly with water about 2 hours before grilling, let it come near room T, and grilled it. I got it too done for my wife, but spot on for me.
I think it works better than typical meat tenderizer.