Thanks very much for your insight. Most of my welding to date has been in the wheel wells and trunk so I was not as concerned about warping.
Yes the door becomes very flat as it moves up from the bottom edge. The rust is not all the way across so I will make small patches to handle small rusted areas.
I will work to replace the bottom .875 radius and back flange.
The back of the door is wide open for planishing and I planned on using a MIG welder.
I was taught to skip around a lot and make small dots to prevent warping, which is contrary to your recommendation of one a continuous to reduce warping.
It appears that there is 1.75 OD mechanical tubing available in .049 wall thickness.
1) Would it be possible to slit tubing and weld to the front skin? After planishing, I could weld a rectangular tube, or angle, to the back for structure.
2) Do you see issues with this approach?
Thanks