I am attempting to install post style curtain holdbacks into drywall. They stick out 4 inches from the wall and are made of cast iron, so they're pretty heavy. After drilling a narrow test hole to make sure there was no stud there, I tried to screw a plastic drywall anchor in, only to have it cause the drywall to "erupt" around the anchor when it was almost all in. I took it out & drilled further to make sure it had room. this time it went it, but the damage had already been done: when I screwed the post into it, the plastic anchor broke and the whole thing fell out, leaving an even bigger hole, and the plastic tip still in the wall! Can anyone suggest a solution to securing these posts? (I have to use the relatively short (1") screws they came with because I can't find longer ones with fine threads that fit into the post end). Thanks.