The only place I've found any rust on this whole truck (besides some surface frame areas that I already took care of with POR-15) is on the very bottom inside lip of the passenger side door. The other door is perfect so maybe Ford didn't prep the area correctly or something...who knows. It's not rotted, just some surface rust and bubbled paint. Theres good metal underneath. Since I had some POR left over, I decided to fix it temporarily until I can run down a small amount of Arizona Beige paint to spray on the area with my little spray gun.
I wire brushed and used my DA sander with 120 grit to get the bubbles off, smooth it off a little and rough the area up some for adhesion. POR wont stick unless it's got some bite.
Degreased and prepped it, masked the outside of the bottom door off with a strip of tape and brushed on some POR. I know, looks like crap but at least it'll neutralize anymore rust and no one will even know it's there unless they look under. I'll get some paint and clear next week to finish it. The POR directions say once its dried and cured you can scuff/sand it up with some 320 grit and paint right over it. I'll let you know how that turns out.