Bending Lower Case back into shape

Yea that's a mess. You can work it a bit with wooden tools, blocks/sticks and rubber/leather mallets squeeze it in a vice (protect the outside with a soft wood pad), Furniture clamps or C/D clamps (vicegrip)

The problem is the more you work it the more brittle it will become (crack or tear)… also it will deform (stretch). You might see if there are any artist metal workers, or a metal/auto body shop that has some idea's & specialty tools

I'd say give it your best shot to get it close… then maybe leave it be…you could tape the edge to keep out dust/dirt, otherwise you'll have to replace the bottom pan.

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