Here I'm forming a trim piece for behind the pilot seat.
I made a wood form to match the curved tube that the piece fits over, then fashion the aluminum over it.
The aluminum is sandwiched between a the form and another similar shaped piece to keep it from moving, and deforming where I don't want it to.
I use a scrap of wood that has been rounded where it contacts the metal as a tapping block.
This way I don't leave pecker (hammer) tracks on the piece that are difficult to remove.