My dishwasher was not getting the cups & bowls clean on the top rack. Checked out for blocked screens, tubes etc. - none. Used dishwasher cleaner - slight improvement. Removed lower spray arm and screens below it. The outlet screen w/chopper was plugged solid with food debris. Cleaned it out. Now reassembling - my question relates to the lower spray arm hub. Do you push it into its seat until it bottoms out or just install "loosely". If I push it firmly into place then there isn't enough thread sticking up to attach the lower spray arm. Any advice would be appreciated. thanks