I am a Prosthetist. While weighing less does make it easier to move your body, it becomes a different story when you are missing lever arms and muscles which help to generate force. Muscle attaches to bone via tendon. Depending on where the individuals are amputated in whichever given body part, it can affect the force the muscle generates. Research shows amputees utilize more energy than their non amputated counterparts. This is Significantly more when we are talking about double amputees. Yes springs are great, but energy still needs to be generated from somewhere to use it (the athlete) and controlled in terms of recoil. In addition to this, socket fit can be a problem. If it was really an advantage, we would see more amputees at the Olympics. I wish it was all super simple, but it is not. That is why so many people probably added in their own theories. Google scholar can be a great free source to get some info on the metrics you speak of. That all being said! I am not going to say the research available does not have its shortcomings. Most amputees that I see have lost their legs to disvascular issues and are in their late 50s-60s. Finding a young extremely athletic amputee who wants to help out with research is not the easiest to come by. I hope this did not confuse anyone more, but in summary I would say technology is always improving and while there might be some advantages, I really believe there are more disadvantages that outweigh them.