That big package from Shapeways contained domes, and I’m impressed enough by the quality of the print, that I don’t think I can improve on them. A coat of primer will tell for certain, but if any sanding is required, it is minimal. Astonishingly, they fit onto the boiler perfectly!
I’m still trying to move the center of gravity back toward the drivers, and so, I filled the steam dome with a chunk of tungsten. It looks like I must have planned this as it fits quite well, leaving about a .5 mm gap all around. The sand dome is pretty close to the balance point, and is only large enough for a lump of pencil lead and a bit of tungsten putty.
622’s domes had a very fine fillet, and I’m amazed that they worked with the 3D printer. A little filling was required here and there where they had not formed a smooth edge. I did the first round of filling with spot glaze putty reinforced with CA. When I was monkeying with the lead weight and putty for the sand dome, I managed to chip it, and filled the chip with epoxy, which worked slightly better than the putty.
One of the things that worked well on #10 was to make the domes removable until after painting. This enabled me to paint the Russian iron jacket and get a clean colour separation with the domes. I took the same approach this time, turning little collars that fit snugly inside the domes and stack and cementing those to the boiler.
Not trusting the actual concentricity of the domes and their collars, I slipped them partway into the domes and stack, applied a little Tamiya thick cement (it dries slowly compared to the Flex-i-file stuff) then pushed them into position on the boiler top. After the cement had cured, I was able to remove the parts, but leave the collars behind.