I need 150mm minimum for ventilation and will provide enough termite protection to negate the need for inspection. The house would be in an area nominated as N1 in the old language. Because of the location of the flooring and the low danger of wind even getting in under there coupled with the weight of the floor, I do not require a tie down. I understand what is says in AS1684 and I would like to use it as a guide, however, a rod is extreme overkill. To stop the sliding I think I will but member against the existing joists and fix them together.