Check out this document for detailed information on optimizing speed: Decreasing load times and optimizing performance: Preparing a Large project in Hype
Only images with ‘Preload’ checked in the resource library will slow the loading of your Tumult Hype document. There should be many duplicates of elements. If you drag an element to your document (which adds it to your resource library), if you drag that element again to you document it will not be re-added. If you’re seeing something different, could you submit a bug from the Help > Report an issue menu and include your document?