Darren, all injuries aside, you lose performance. If you have them super loose you're more likely to have your heels lift on a toeside cut (less response) and the same for your heelside cuts. You will have waaaaaay more control of your board with less effort if you wear them properly. Injuries are going to happen, no matter what. You can't stress over it and the best way to prevent it is to go to the gym and strengthen your body. Letting your boots be super loose is prolly increasing the likelyhood of an injury. Just get out there, cinch down and have a good time!