Why not just heat it and gently hammer the swell down.
How to shrink aluminum sheet metal.
Could also add some shape around the holes with offset roller or hammer form.
Hot shrinking is the legendary shrinking method of simply heating up and dashing water for a quick chill.
You could do it with a hammer as well and a groove in a piece of wood.
Then remove the tool and move it over so the fork will roll the metal over the other side of the fork by twisting the metal the other direction.
If you have access to a bead roller roll yourself a bead and shrink it.
How to shrink aluminum step 1.
Put it in a bead roller and put a small bead though the middle to take up the stack and add some shape.
This will create a cold aluminum area or a hard steel one with very little resulting shrinkage.
Place your aluminum sheet onto a work surface.
Get used to this idea and your abilities will grow.
Heating up metal and throwing cold water on it may shrink it a tiny bit but it makes distortion and hard steel.
Do not over heat the steel.
Heat to blue only and shrink that much.
Start by inserting the fork into the edge of the sheet metal at the desired depth of the shrink you want to make.
This works the other doesn t.
Heat up a quarter sized spot on.
Slide on a pair or leather work gloves safety glasses and a dust mask to protect your skin eyes and lungs.
Then twist the handle of the tool to twist the metal around one side of the fork.
Get an idea of how much heat it takes to cherry the metal and how hard you need to strike it to smooth it down.