I have a cinder block wall/chimney with a galvanized steel chimney chase cap on top. It was poorly installed and looks like it is rusting. I am looking to get it replaced and have been offered a couple options. 1. Replace it with a stainless steel cap or 2. pour a concrete cap over the existing cap and seal it that way. I am trending toward the cement since it is significantly cheapr but have not heard of doing this. Also, they say they cannot cut the flute as that will void the fire warranty so installing a custom cap may be more difficult. Any ideas/advice on this problem?