Update. Started on the main body.
Decided to add a fuel inlet which will actually be the smoke unit filler tube  
 
And primer
Mean while had a little play
https://www.youtube.com/watch?v=PHRkF2FxnN0
Then disaster  :BH 
One of the track drive sprockets came loose so a strip down to get to tighten up the grub screw  :AR