Hi David – thanks for joining the 2020 forum and posting your question.
There are a few reasons why a design file can become very large:
– Many examples of SketchUp import files within the design (perhaps these are the graphics you are referring to)
– Large ‘Design Attachments’
– Textures/materials imported for the specific design – the imported file size could have been very large.
If none of these suggestions resolve your specific circumstance, please contact the 2020 Fusion Support helpline, who would be able to provide you with further guidance or review the specific design file with you.