Jonathan's Modern Image Workbench (3D-printed class 323 EMU, class 156s, 3-car 144s, a 141, 4-car class 465s)

[tjf4375]

My bad sorry, I should have read the thread more carefully. Yes I'd imagine it's difficult to get predictable and controlled results with heating, as it may straighten some areas and cause distortion in others as the plastic cools. 

May be easier to cut your losses, but I appreciate that's easier said than done when you've invested a lot of time into it. Hope you find a solution one way or the other.

[JDW]

Agreed, I don't want to write it off, and the other two cars look like coming together a bit better. It's never going to be a high quality model, but is unusual enough that it seems worth carrying on with. Certainly, I'm not going to be spending a fortune on more parts, I doubt I'll motorise it, and it'll probably just get a cheap plastic pantograph. 

 

I have some heavy weights, the metal strips from Lima locos of old, I wonder whether immersing it upside down in warm water and placing those lengthways inside the roof, spreading the weight as evenly as possible, might work, but worry it'd do something awful to the sides then instead!

[tjf4375]

That could work but yes you are going to have a problem with the sides. As it's all one integral piece, any distortion of the roof will likely end up being mirrored in the sides, unless there is something there to keep them straight.