If it were my stone I might do a square bar cut. Simply because I think a bar cut would help that c axis.
But a Portuguese round might be fun. I have cut Portuguese on stones as small as 4mm. It’s hard on smaller stones.
I did a round checkerboard once too. I think I got the design from Bob Keller’s site. That one would probably look good in the tourmaline.
You could also try a honeycomb cut. I don’t personally like honeycomb, but that’s preference.
A whirlwind might be nice too.
Just my two cents for what it might be worth 🙂