Modified the driver from FET + resistor to 7135x4.
Removed 2 x FET and 3 x resistors
Put in 4x 7135 regulators in parallel (3 on board, 1 stacked)
Connected the MCU PWM pin to 7135 VCC
The mod looks very ghetto, but it works and is minimally invasive so it is fully reversable LOL. The only thing you need is a couple of 7135 regulators and a pair of steady hands.
Lost lowest mode due to 7135 slower response with fast PWM
Tested output current with 519A 5000K
D10 7135x3 modes
0 0mA -
1 10mA 3lm
2 170mA 52lm
3 440mA 140lm
4 1070mA 330lm
D10 7135x4 modes
0 0mA -
1 20mA 6lm
2 200mA 65lm
3 560mA 187lm
4 1310mA 430lm
Now it has fully regulated output and is fairly efficient. At under 60% battery capacity it is actually brighter than stock FET setup and now at level 2 it gives 65lm regulated output for over 17 hours and level 3 187lm regulated output for over 6 hours with a 3400mAh battery. That is a lot better than stock where at full battery it runs hot and the output keeps dropping.
Level 4 (highest level) has a timed step down of 5 minutes from 100% output to 50% due to MCU programming. Level 3 is 40% PWM, level 2 is 15% PWM and level 1 is 1.5% PWM effectively with 7135 turn on delay. The mode spacing is pretty good after mod.
To me the modded driver output is better than most budget headlamps on the market. Alone with a 519A emitter and TIR swap it beats 90% headlamps in terms of real-world usability IMO.