If there are actually low spots next to the high spot, it would be better to try and raise them up, IMO. If your panel has the right shape overall, It's better to bring the dents out than lower the areas where the metal is exposed. Do you have a piece of straight sheet metal you can lay over the panel to check the profile? Or a thin long ruler laid flat.
If you have low areas that have been stretched, you may need to shrink them some. A donut dolly (I use a PVC pipe coupling) and a body hammer with a slightly domed face can do the shrinking.The stretchers behind that back panel are often in the way, and one of your high spots looks to be right near one (right side of the window opening). I've found that the back panel is one of the hardest to get straight, and they do take a beating.
I see you're pretty close to MPandC (Robert) down in Leonardtown. You might try contacting him by PM and see if he could drop by and advise you. He's the metalworking guru on here.
