Saving a partially machined part as a solid body

Saving the workpiece as a solid:

You can save the simulated workpiece as a solid and then import it back in, for use as a stock model for subsequent operations. You might argue that "rest machining" might accomplish that but I don't know if you'd be 100% right.

There have been a few Youtube vids showing how to do this. Here's one that is short and to the point. Slight issue here being that it didn't work for me. I suspect Autodesk have changed something. 

This is what worked for me:

1. In CAM simulation, save the "finished" model as STL. Right click > Stock > Save stock. You don't seem to need to specify the file / model type.
2. Change to the Fusion Model environment, import the STL by selecting Insert > Mesh. Rename ("Stock body" etc), as required. NB: Ideally, open a new file to do this - you must turn off the timeline for the "STL to BRep" option to appear in the Model environment.
3. Reduce the size of the STL file (in the Mesh environment, Modify > Reduce). I reduced it to 0.05 (ie 5%) of original and it lost very little noticeable detail.
4. Convert from STL to BREP: Modify > Mesh > STL to BRep. You now have a solid body.
5. Import this new body into your working file from the Data Panel: "insert into current design".
6. In the CAM environment, you can now select this body when specifying the stock for the next operations. 

Sounds simple enough but the struggle at this point is getting the toolpath to stick, not the stock model. I suspect I'm going to have to simplify the model by filling in holes etc.