I have always heard that brass likes to be drilled with a drill bit
with no rake on the leading edge. If the bit has rake, the bit wants
to screw itself into the brass. I have always ground the leading edge
off my drill bits (the leading rake angle is parallel to the length of
the drill) when drilling brass, with remarkably better results than
the factory points.

Sooo...With this in mind, I would grind the leading edge of the
milling cutter to a zero rake, i.e. parallel to a line through the
center of rotation. This should keep the cutter from grabbing and
trying to feed itself into the work, resulting in a more accurate cut.
I have never milled a piece of brass this thin, and would be
interested in what you discover in the process.

Brownnsharp