OK so, here we are again after getting distracted by work. "Work is the curse of the drinking classes" (Oscar Wilde).
The next job on the instruction sheet is relatively simple, involving part P37 (the buffer beam inner frame)
and P41 (the beam overlay):
What the instructions don't tell you is that part P37 has to be folded according to the etch lines at each end of it:
This followed by P41, the overlay which needs to be soldered over it:
Remember that the square buffer bases must be at the lower edge of the overlay, not the upper! You only need to flow the very minimum of solder, because the next job is to fix the completed buffer beam to the footplate you made earlier. It takes time to make sure you've got it all in line, and the back edge of the buffer beam "sandwich" must butt up against the front edge of the footplate valancing:
Again, only the minimum of solder should be flowed into the join - and it's best to run it from the inside (or behind the beam) so that you don't get solder going all over the rivet detail: