While out on a ride with one of my ‘Niner friends, he got a flat. The new tubes stem busted when it was getting pumped up. This was the last 29in tube in our bags. We did have an extra 26in tube, so we used that. We had about 30 miles to get home, so we hoped this would work. It was all dirt road and asphalt home, but the dirt road had lots of rocks and other tire damaging objects. Amazingly the stretched and held air all the way home.
It’s good to know that a 26in tube will work for a 29in tire