I am undecided whether to choose a 50x50 2.4m or 65x65 2.4m galvanized steel posts to support a 1.8m high hardwood lap and cap fence with 3 hardwood rails. Anyone know if the 50x50mm posts are sufficient to hold the weight of the hardwood pailings and rails, especially during windy and other harsh conditions? Budgetwise, if I can only buy 50x50, is there a cheaper option to strengthen the fence. Thanks.