Outer Limits 4x4 Board

After having to weld an extra gusset to the inside of my cab for engineer's the back panel still on its bowed out a touch

to "pull" it back in, I know a mix of heating it up and cooling it down quickly will work. just unsure of should I be applying heat and cooling from the inside or outside for best results?

I'm gunna have a couple of practice shot's but any hints or tips from people?

Cheers

Simon

Get a sponge or cloth and a bucket of water. Apply heat with an oxy to small sections of the the high spots (until almost cherry red) then hit with sponge to shrink. work in circles around over the area you want to shrink.