Actually Niall, generally speaking, larger spurs indicate a male. However this isn't always consistent, and probing is necessary to guarantee correct gender.
When looking at spurs for sexing, don't go off size, size is an indication of age, best go off shape, and where they are on the snake, males spurs sit slightly further out from the vent, though this info is useless if you arn't used to looking at spurs or have another snake of different sex to compare against.
Its actually the hook on the end of the spur that gives away a males identity.
Both males and females can have large spurs but females always lack the hook,( for lack of a better word), on the end of the spur.
hmmm.... all this info is just confusing lol. mine has VERY small spurs and seem to be very close to the vent. the only way i can even see the ends is to get hold of his tail and gently bend it back. is it more dangerous to probe when the snake is bigger?