Help with bike light mod

Hey guys new to the site. I been doing some reading the past day or two about getting some more lumens out of my bike light, and before I buy the parts I need I wanted to get some advice. I not sure if this will even work so I'm sure someone here will tell me I'm wasting my time if it won't.
Here is the light It's cheap $20 I got two of them.
viewpoint flare5 5 led
runs on 4 aaa wired in series I measured 6v coming out of the battery pod
50 hour claimed run time

The plan to put two 10440 cells in this thing and run 7.4v
So will it work?
350 mAh doesn't sound like much, how much run time can I expect?
Any specific brand you guys recommend?

Thanks