In that case I agree DD is probably too much. The LD3 might be your best choice. You would need to heat sink the FET (s), and this might add quite a bit of challenge to the build. To really heat sink them well you would need to remove them from the driver PCB and make a good heat path to the flashlight body. I have done a couple builds where I’ve used the FET in its linear mode (as the LD3 does) which makes the FET dissipate a lot of heat. See these for some possible ideas:
Buck driver(s) could be an option, though I don’t know of one that would work off hand. But they would probably take a lot of space and might not end up being any more efficient than the linear FET route.
Edit: DD/FET with added resistance is still an option, and would be much simpler than the above options.
In a DD situation, if one of the LEDs died (became a short), the others would less than 8A each.