The mistake the designers of this thing are making is to try to have the rider in the same posture he would have were he riding a motorcycle. That's the wrong posture for a one-man flying device. The center of gravity should be lower. The flyer should probably be in a semi-reclining posture, similar to what a rider is in on a reclining bicycle. Also, if I were designing one of these, I'd put up protective guards between each prop and the pilot. A section of cage made of heavy wire would be enough. If one of those blades comes apart it could skewer the flyer.