the guys that taught me to use it said the big swing, making sure your back rounds at the bottom each rep. you're also not using ultra-heavy weights either. it took me a while to get it, since i'm just so used to making sure my back NEVER opens like that.
Yes, it is a bit intimidating at first letting that weight drop under the “table” with your feet attached to it. If someone had just described to me how to do it, I would probably never have tried it without first seeing other people do it.
You can envision some really bad things happening, especially like you said, with the back rounding like that.
Is the reverse hyper bench public domain, or does someone specific own the rights to the design?