I actually was wondering this myself a few months ago, and I made a table of wood strength to weight ratio, just pulling numbers from
www.wood-database.com. I got these numbers simply by dividing the modulus of rupture by the average dried weight. My thinking was, this would tell me the woods that could be the lightest without breaking. I can't vouch for this list as being a good indication of siyah woods, as I imagine there are many more factors to consider, but it seems like a good place to start.
Higher numbers are better:
Bamboo
356-461
Black Locust
404
Jatoba (Brazilian Cherry)
395
Katalox
389
Pignut Hickory
387
Black Walnut
384
Bloodwood
383
Ipe
372
Olive
363
Hard Maple
359
Ash
357
Poplar
348
Osage Orange
345
African Mahogany
330
Red Oak
327
White Oak
316
Inspired by this list, I made some jatoba siyahs that worked out great. They are quite extreme, are about 1/4 inch thick, and have no stability issues.
There's a super thin layer of osage on each side of the tips, with the grain at a 90 degree angle to the jatoba.