Bought a nice smaller J&M wagon from a retiring farmer to use as a base unit to reconstitute/revamp my old plastic fertilizer auger for seed to fill the planter. The previous owner recently had it sandblasted primed and painted and it has brand new tires /tubes all around.

 I've tracked down most of the missing pieces and parts I needed from the original supplier of the plastic auger. The originals I had were consumed from using fertilizer and got scrapped a few years ago. I've made a few customized brackets and supports to tailor it exactly to this wagon the way I wanted it and from memory of the original brackets

The supports extending cross ways over the runners have been cut off an reinforced at some previous point with heavier angle irons out to the upright angles where the door moves up and down.

The only drawback is there are a few thin spots and holes just inside the door in the corners.

There are a couple angle iron pieces under this thinner skin for support which are in good condition. The small vertical triangular piece is in a tough area to get to and sandwiched behind the additional angle on the outside of the box.

So the question is what is the best way to make a solid repair. Cut the entire sheet out across the width of the door and put in a new piece as well as replacing the small vertical triangular pieces in the sump area ?

Or cut some small triangular pieces to cover the bad sections of the floor area that are thin and replace the small vertical triangular pieces in the sump area ? Something like this cardboard pattern illustrates.

In this scenario would it be okay to lay the repair pieces in over the top of the existing pieces and spot weld the edges and perhaps plug weld above the areas where the angles runs underneath ?

My main concern would be corrosion between sandwiched sheets ? I'm guessing a weld through primer would be a good move on the back side of the repair pieces ? If so who makes a good weld through primer for this application ?

This won't be seeing any fertilizer use only bulk seed beans to fill the planter instead of 5 gallon buckets. The repair areas won't see a great deal of pressure on them but they need tightened up or they will be leaking seed. The smaller vertical triangles will be the toughest as they sit back under the other pieces that make up the sides and bottom.

Still test fitting and customizing things but this is how it will eventually come together.

Any ideas or suggestions on the sheet metal repair and weld through primer recommendations would be appreciated.