I'm not sure I buy into the float idea fully. I am tall, lanky, played a lot of basketball, and generally have great knees. However I feel fine with my Shimano M520. In fact, I feel very odd with the slight amount of float that exists. I prefer to find an angle that is in-line with the pedals and stick to that, float makes my knees feel wobbly and not secure. I'm not sure how to explain it, I would just say it's a personal thing. I don't know if it's worth returning the pedals before trying them though, you may want to give them a shot.