Neighbour has one as do I, his one has grown out over the footpath, so he's ask me to use my petrol hedge trimmer to cut it back. No worries. Now he wants to leave it in case a hard cut back kills it. Will it? I have an Escalonia hedge and if I have cut back to hard, leaving just bare branches, Sun causes bare branches to leaf out. Not sure if Corokia will do the same. His hedge is about a metre wide and 900mm high, need to be cut back about a foot. Yes it will be very bare, but if it regrows well aided by Nitrogen, it may be worth cutting less, back past the leaves but not too hard, then let it fill in then do it again?
Edit: one side trim not the top