One of the great frustrations in researching pools, is that you hear lots of bad advice. I am told that even the best galvanized walls will eventually rust, especially if they are scratched. Also considering that chlorine is corrosive, and that the resulting pits & surface irregularities can be hard on a liner,.....and I am leaning toward polymer. I have also heard that polymer is harder to set up. Any help from the pros on this issue?