"As @TrippyLighting says, the dimensions used during sketching\modelling are rarely the dimensions you need for manufacturing documentation". I am not surprised he would say something like that. Well, I have lived and worked here in the Silicon Valley since 1974. At no time would any engineering department that I worked for, or ran, hire anyone with that mindset.
If I had a designer who spent all the project's money and time to created a model that was not going to be anything like the final proto, I would fire that person and hire someone who knew what they were doing. I am not sure how things are run in your countries, but here in the Silicon Valley you do it right the first time or the competition eats you lunch. For my money, I want total consistency and continuity between the Model, the Drawings and the Production Prototype. If there is a change, then we take the Model to Rev 2. If you don't do this, you don't have a legitimate documentation system.
And you, the Senior Principle (Spelled Principal) User Experience Designer, you better get with the - real life - program or this Fusion program of yours will be a total failure. People in the real working world here in the Silicon Valley have no time to waste on re-do's. New startups have seed money. That is it. When that is gone, they are gone. You do it right the first time and ahead of schedule or you are thrown out of the car at 90mph. Never forget that.