Weld representation - I decided to use a temperature controlled soldering iron (it's an old cheap one, cunningly voltage limited through a light dimmer). It has a copper bit which has been filed to a chisel point about 2.5mm wide.
The light dimmer doesn't seem to work at the moment so I resorted to turning the iron on and off - use a bit of scrap plastic, get the iron hot enough to just melt the plastic and then turn it off and use it on the tank body. once it stops making an impression turn it on and repeat the process.

It pulls up a lot of plastic which looks scrappy, but after sanding it looks good - see the welds on the engine cover.

Also added the strip of armour under the mantlet.

Jo