It looks like you had the fire tubes bound together in this last spring operation. Did you have something in there too keep the ends separated of did you bend them apart after pickling? Anyway, thanks for putting in the effort of recording the project!
I lightly wrapped some wire around the top of the tubes just to keep them together. and avoid me catching one's on the outside. They are then gently straightened apart again ready to line up with the front tube plate using a piece of bar the in full length of the tube to tweek each one. With the bar it moves and supports the whole length of the tube. If you just try and position them from the top without the bar you can tend to just create a bend in them.
Meant also to say although I added a small shoulder to each tube to stop them dropping in the fire box tube plate there is nothing to stop any movement in the vertical with the outer tubes.
The boiler wrapper is 16swg as the guidance says. The outer boiler shell is also 16swg. Ideally 18swg is fine but can't seem to get hold of 18swg 2ins dia copper tubing any more
