Using two 3.7v 16340 cells in the PD30 is a baaaaad idea. The input voltage limit on that light is 6.0v. Two 16340 cell will output more than 6.0v. If you use two 16340's you risk of frying the circuit, sooner rather than later. That's the least worst outcome. You also run the risk of starting a fire. That would be bad. Very bad.
Safety first.