Fantastic work!
I had to laugh when I saw your scanning of the Monogram transaxle.
I ran into the same problems recently with the Valkyrie engine cans. I had started to model the part when I realised that the hoses and other features on the radial surface would be difficult to measure, and best captured by scanning.
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I have a rudimentary David Scanner setup and figured it might get something usable. The part is so small though, and thus far I have found it too difficult to date to get a good result.
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(Above) Multiple scans aligned in David Scan.
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(Above) Scans merged to an mesh result.
Its almost there for my requirements but not quite. Hence I have put it aside for the moment, and have gone back to the Centurion with traditional verniers and paper print validation as per your excellent blog.