I called this a medium Freighter, but this one is fairly large. It is the long "neck" and Star Trek variant of the design. The underside of the neck is where cargo modules of varying sizes attach to the ship. Includes the capacity to carry a starship, such as in a rescue or salvage operation or to deliver a starship hulk to whatever destination. Pictured below are 3 variants. The far right shows the ship loaded with a large cargo module.
These are good, You should check out Sketchucation.com, It's free to join, and there are tons of developer and utility plugins, it's pretty much all free, they have a plugin that you use to automatically install the plugins from their site! My sketchup UI looks a hell of a lot different than the base program because I use so many plugins. Sketchup can be a powerful program if you are willing to put in a little time, those designs have great potential and if you check online you'll find thousands of Sketchup Tuts, I have been using this program since Version 3.
Thanks! I've been looking at sites like that and also the tutorials on YouTube. These are the latest version: This again showing the area where cargo modules connect to the ship, or where a ship itself can be docked for repair, salvage or transport.