I am building tables... really nothing too complex. Just gonna put some corrugated roofing on top of some wood, have it at a slight slant so the water drips down the roofing, and into a gutter system. The roofing that I got is metal, and I was told at the store it won't create hot spots but I just don't see how that's possible and I'm thinking I may have made a mistake. It's metal, so how could it not create hot spots? Anyone use it? I know people do but I'm trying to avoid putting anything into my garden that puts me even remotely at risk.