Hmm....I'd have to go for the metal
I made stuff today. This is where my heart is. I REALLY like the challenge and I don't get to shape much. As I dig into these frames, they are bad. I'm dedicated to making this scout 100% rust free so this is going to be a toughy.
First, I start with a flexible pattern. The paper is an actual representation of the shape of the pattern, including bends...
I have lots of different gauges of sheetmetal I keep on hand. I sneak it in when no one is looking

That's the harbor freight electric shear I use to cut off pieces. I think I've covered that before...
I wash the sheetmetal with lacquer thinner to keep the oils and dirt off the markers and tools. Then I make an accurate trace of my template...
Then I wheel the contour into the panel. This is not a compound curve, so it's easy. You "could" bend it over a pipe in theory.
Then I bend the side that will be contoured. You "could" used the edge of a table...
I take the contour of the frame with this cheapo contour gauge...
That's are cheapo harbor freight shrinker /stretchers. They work best when your flange is 1/2". Stretch too much...Shrink it back. Shrink too much...Stretch it back out. Contour match below...
In theory, you can't stretch with metal on metal hammering alone. Like this....
When trimming down flanges after the fact, I use these for accurate lines...
At this point you have a template with lines on it where flanges are to be bent or shaped. What I do at that point is to cut the template down on those lines to mark the steel for the next step. The template gets progressively smaller as each additional part of the panel is being marked...If that makes sense.
I use the bead roller to bend over flanges that have contours in them in several passes...
To be continued...