I would guess that if your child's birthday is on 2nd of January you would be very keen to keep the current system, but if their birthday is 31st December you may well take a different view! Hence the call from many for age on the day races, it does seem a fairer system, but causes difficulty with championship series. Perhaps one solution which would go some way to addressing the concerns would be for the championship age grouping to be the date on which the first race of the series takes place?