FYI - crucial to keep the pelvis tucked and NEVER lose tension. Two very strong traines I know have jacked up their backs on the wheel. I chucked mine after doing it.
IMO - walkouts are safer. Stand like you're going to touch your toes. put your hands flat on the floor as far away from feet as necessary. Start slowly walking out your hands till you're like superman, MAINTAIN TENSION, then walk the hands back.