The beginning of this post is 1241: Bell Frame (pt 1) which covers most of the work that was done. Whilst the metal work was away being powder coated, the board was finished and varnished. What I end up with, is a whole pile of bits to be reassembled on various instruments.
I was asked about the strength of the hinge and the boards flexing under body weight in a comment on (part one). The main bar around which the whole step rotates supports the front edge of the forward board, and there is a steel brace to support the outer edge of that forward step.
The new extension board has braces running across the width of the board both fore and aft. These braces also provide the pivot points around which the legs rotate.
Below is a short video showing how it all works.