In the late 60's we were one of the first schools to have a Cloud 9. It was very dangerous. Lots of injuries from the visiting PVers. They had never vaulted on one and no matter how many times we told then "you have to land spread eagle", they would try to land feet first and roll to their back. Before they could roll, they had bottomed out and hurt their foot, ankle, leg, hip or something. Very "unsafe" but we usually took all the points for the vault - they were out during warm ups

Very dangerous.
Dan