Greetings: Flat springs were no problem for me when I was building
the Roy Norman organs.  We have a large commercial lumber yard near
us that has their lumber brought into their yard on train tracks that
go through their yard.  Some of the really big beams come in banded
together onto the flat cars with really big banding made of a high
strength tough very springy steel.

I got a carbide "spade" type drill bit with no helical flutes.  You
don't want the drill bit to grab the banding strips when it breaks
through as this is dangerous and could break your carbide drill.
MSC is a good source for carbide spade drills, and not costly.  You
can cut the banding with the edge of a grinder.

Cheers,
Robert Leber
Fremont, California

P.S.: The banding was always free for the asking and more than
I could ever use!