Ok. So the Icr16340 from Keeppower have a max discharge current of 2c, meaning 1600ma. Is that correct? Still not great at the numbers thing
that's a protected cell, if you try to do something silly, like overdraw or overcharge it will just shut down. Come to think of it I had my M91 sometimes cut out on the 2x18500 configuration, that's why I went back to 3xCR123 configuration on that one... Which is, by the way, the more dangerous solution as that way I'm circumventing the protection circuit by using a battery without them, but still, it was designed for that setup and worked reliably for the past few years, so no worries there.
An alternative would be to use some good quality unprotected 16340 li-ions, that way you'd never hit the protection circuit, while still somewhere inside the maximum load. ( also that way you'd need to watch for your cell charge, to don't go under 2.4V / battery ).