An evening of revelation. In an attempt to get more light onto the areas we were working we decided to try and turn the body around. Why hadn't we tried this earlier? The results were great - so much more room to work and much more light as well. Marvellous.
After that we fixed the rusty hole just above the last patch we put on. I cleaned it out and ross made a beautifully crafted replacement...
... and welded it on.