A comment I'd like to make, noted from an article I re-read recently about building a loco.....and in NO way meant as a critiscm of the 4F...far from it...but may be of use to others reading this thread....I noted the author's emphasis on achieving straight and parallel lines........things like, handrails, pipe runs, footplates, etc.
I suddenly realised what spoilt so many of my efforts in the past...things like, handrails with a small kink, or an un-noticed but gentle curve?
pipe runs which weren't parallel with things they were supposed to be parallel with....even handrail knobs which weren't properly positioned on either side of the boiler.......
it seems so very important to get these things right??????