I think it would best explained by a Rotax tech George - I am not much good beyond changing the oil - but he stressed on the phone 'Don't put a nut on it and fly!, it will cause damage!" and he did show and explain it when fixing it but in one ear and out the other. I do remember him explaining that the rather long stud/bolt is designed to spread the load evenly over the hole length - however that doesn't answer your Q

cheers

ross