A 400lb bag hit into the ceiling!!! Never seen anything like that and I am very skeptical. I have watched a very big Kyokushin fighter with some the best power I know, absolutely rattle a 400lb bag but thats it.
But you know, according to Bruce Lee's friends, Bob Wall and Wally Jay, he can kick 300-350 pound bag flying and then thumping the ceiling. Just read the description above. But I don't know if they are exaggerating Bruce.