Hi, I have an 18×33 above ground pool that uses SWG for chlorine. I have recently noticed that I have some severe corrosion on the galvanized steel upper connecting plates that the rails screw to. I am worried that if I start replacing them one at a time, the walls might bow out. Question – are the walls stiff enough to maintain the integrity of the pool if I replace them one at a time or do I have to partially or completely drain the water? Thanks