The original tapered boiler course took about a week of fitting, filing and filling before it was acceptable. Now, the process to draw the shape may have been painful, but cutting it out with the Cricut took all of five minutes. Because the two boiler sections are actually quite accurately formed, it took very little filing and filling to get the new course into place. Not only that, but now I have the pattern to cut out tapered courses for 622’s sisters.
Pembroke:87 
Hi René,
did you think of printing the boiler?
Regards,
Andy
Yes I did. When I started on 622, I was using Shapeways, with no way to control layering or orientation, so it was a non-starter. Maybe now it is worth another look.