I have no problem with not being able to fit the 2.5m parts into the shuttle. I think it should be used for what it was designed for, and that's the smaller parts and parts helldiver is currently making, service missions, small satellite deployment, and crew rotation. If you really need to get a larger piece up to your station or just orbit in general, rockets will work just fine. Like Westi said, the inflatable parts would be a perfect thing for the shuttle to bring up to the station if you're bent on using the shuttle and having larger habitation modules.