Starting with the rear wall, I first had to cut the bottom of it to suit the new floor profile. Used the board I had cut for bending over the flange as a template. Had just enough metal after bending flat the old flange. The 48 wall however is not flat long enough in the middle for the wider window that I will be making. The 58 wall was, but was in poor condition, so using this one.
Need to remove the brace to flatten out the wall. This will also give me a good chance to treat the rust as well. I found that adding a little pressure, using a cold chisel in the join, as you use a pilot point drill on the spot welds, helps stop you drilling through into the next layer as you feel it 'pop' as the pressure is released.
To treat the rust on the inside of the hat channel, I left it for a week in the white vinegar and citric acid mix shown earlier in the write up. Came up very nicely and will be coated in weld through primer before re-assembly.
I got the brace straight using gentle pressure from the press and hammer and dolly work. The paint on the panels was stripped off using a strip it disc on my 7" sander. I try to take a layer of paint off at a time and move around on the whole panel so it does not heat it up.
The panel came up like new on the outside, but the part of the wall hanging below the floor on the other side still had rust pitting that would not come off. Will have to make up some thing else to dip this as don't have enough vinegar solution.