Just wondering how much of a difference there is in the skill and fitness levels between 5s and 4s. I am getting ready to upgrade to 4 and am wondering what to expect, since all it takes to get to 4 is to compete in 10 races. It also seems like there has been a wreck in half of the Cat 5 races I have been in, and I am guessing that this is because 5 racers are just squirly and inexperienced. Are there as many wrecks in 4, and how much more fit are the riders?