The competition is all about propogating a coral and learning from the experience - not about the size of the coral.
If you can cut it in half and get both to survive and pass one onto a fellow hobbyist then you have prevented one coral from being removed from the wild - that has got to be a good thing.
Slightly off-topic, but I was recently reading an article which indicated that larger acro frags (5cm if I remember correctly) had a significantly greater chance of survival compared to smaller frags - smaller is not always better.