Well ... 3 weeks since the last update, and there isn't much to show for it. Having got the mechanism and footplate sorted and painted I started to fiddle with the boiler/tanks casting, but the more I fiddled, the more work I gave myself ...
I started by building up the underside of the boiler between the tanks, as it looks from photos to be a bit exposed, and I think the standard SM has a retaining spring for the motor, which goes in that space. I didn't have this spring, and used 2-part epoxy to hold the motor in place. I used GreenStuff to do the building-up, with no great problem, leaving a gap for the worm but hiding it.
Next I sanded the underside, as instructed. The GreenStuff needed a bit more removing than the rest - a bit over-enthusiastic on the previous stage - but I put a sheet of fine emery-paper on a sheet of glass and rubbed the casting down until most of it was flat. However, the rather flimsy cab sides still had a gap below them - in fact, the bottom of the sides sloped up towards the rear, and I didn't want to remove too much of the rest of the casting to get them level - I could stick on a bit of syrene strip and sand that back to level it all up. Having got the casting flat it also became apparent that the tank fronts weren't vertical, so there had to be a bit of delicate sanding there, too.
The cab sides also had a tendency to bend inwards, once I'd removed the piece of card that had protected them in transit. I looked up 'straightening resin castings' on Google and found this site http://www.sylvanscalemodels.com/modelling.htm#Warping
All seemed very straightforward, and I lashed up a cunning arrangement of MDF blocks, rubber bands and C-clamps to hold the cab sides in the position of required straightness, ready to give the hot water treatment. At first I put the casting under the hot tap, but when the clamps were removed the cab sides sprang back to the bent position, so I tried boiling water. The sides did straighten but, being very thin, bucked like pieces of well-done bacon. After a few futile attempts to straighten them I cut them off, and plan to fix styrene cab-sides in place later.
However ..... while the thrashing around, juggling with blocks, bands and clamps was going on, the beading on the tank sides started to break off on one side. When things had calmed down I tried sticking the broken bits back on, but that looked awful, so I decided to remove the beading completely and replace it in due course with styrene strip. The beading on the broken side came off easily - mostly - but the other side was of sterner stuff and I had recourse to a sharp blade to slice it off. Of course, the tops of the tank sides ended up slightly less than level, so the next cunning plan was to fix styrene strip along the tops and sand it down level as required.
And that is the current position, with a sadly mutilated casting - but at least the tank side tops are level!
I've also marked where the chimney and dome will go - I'll fit them with a piece of wire fixed into a hole in the casting to get positive attachment. I've started to make the new cab sides, and fitted little pieces of L-section to them to get a more positive attachment than a plain butt-joint. I don't know how much work I'll be allowed to do over the Christmas jollifications - it may be a while until the next update ....