I don't do competitions either as I think that they are unfair.I don't think limiting baits will work.Boaties had a comp up here recently that was limited to the size of fish I do not remember the deails as I am only into beach fishing but what I can recall it was limited to something like 32-38cms and 4 fish per angler.I don't know how the prizes were won but I suspect it was the heaviest in that size range.This could be a good idea for surfcasting comps as well.This would make it a lot more even for all competitors being local or not.