Technical Straightening a warped panel

Putting together a '29 closed cab pick-em up truck. The back panels on the cab are pretty straightforward; essentially a square with 4 mounting flanges (picture a shoe box lid) and some bead rolled (or stamped) details. I have a pair of replacement panels (two pair actually), and all of them have a "twist" to them, making cab assembly quite interesting. Two of the panels came with the other parts, and unknown maker. The other two are from Brookville, but admittedly, they didn't actually stamp them, so I'm not trying to bash their quality in any way.

As to how bad; the worst one is pictured. With the bottom and left edges flat against the door, there's a little over 4" of deflection (last pic).

Any tricks or tips on how to make them lay flat?

 

No tricks install it .

 

as above, assemble, then see if anything is wrong.

 

Anything you do to it now will likely cause you more work and grief, install it then if it oil cans do some judicious streaching

 

Yup. Just bolt it together, then let us know what you find.

 

As soon as you attach it with fasteners, it'll be flat.

 

My concern I guess, is that it is both upper and lower panels to deal with at the same time, doubling the effect from top to bottom, with regards to overall twist. Guess I'll give it a go and see what happens. I'm fine with not "fixing" it and making it worse!

 

Tommy Chong used to often say: "Go ahead and try it man, Ya never know"

 

Try this.......
Lay the panel in your photo flat on the floor.
If any corner(s) stick up higher than the rest, place a fingertip on the "high" corner(s) and press down with a couple of ounces of pressure. (If a diagonal corner raises up, press lightly on both. No big deal.)
If the panel flattens out, that's the way it will attach when it's in the truck.
If you need to stack 8 bricks, your left boot, and a box of C-clamps to get the high corner to lay flat, send it back.
What I see in your photos looks quite normal for unmounted panels to me.