An initial test assembly of the mast revealed that the parts were not a perfect first-time fit. It was clear that some tuning was required.
The problem was that the rebates needed to be cleaned up.
These tools did the job.
This little bullnose plane is great for getting into corners, with its bullnose removed.
The last time I used it was to clean up planking rebates on the first boat I built, forty years ago!
A second and successful test assembly followed. It looked like this.