Tip thickness on "Ishi-pyramid bow"

[Acheulean]

I'm working on a bow similar to the "Ishi-pyramid bow" on page 126 of TBB Vol. 4, and I'm wondering (approximately) how much I should thicken the last 5 inches of the tips to keep them from bending. There's no Eiffel-towering or anything, just a pyramid taper from the handle to the tips. Would an extra 16th of an inch be sufficient, or do I need to go thicker than that?

Thanks

[simson]

it just need to be 1-2 mm thicker to stiffen

[Acheulean]

Thanks Simson