Last spring, I caught one of our little mighty munchkins doing something like a cross in between the hall. She pressed both of her hands into each side of the wall and was about 30 degrees above cross. I think Isabel was around 7 or 8, training L5. She was one of the strongest girls we had.
Doing something like this isn't nearly as hard on a non moving surface than it is on rings. I've seen a small child, kinder age do something similar in his grandpa's arms while I was at his house and working on his computer. I told of my gymnastics background since his business was where the first gymnastics gym I worked at was and we got to talking. Eventually I ended up doing his systems at home one day.