So I bought a Danby 8k btu window a/c unit today to install in my wife and i's bedroom since our house has no central air. I get it home tonight and open it up, start reading the instructions and figuring out how to install it. There is a top "L" bracket that installs on the top of the unit and the window is suppose to slide down into so that it holds the unit. Well our new Anderson double hung windows are about twice as thick as what this "L" bracket is designed for. Is this a common thing with new windows? We're these windows never designed for an a/c unit? Any help would be greatly appreciated.