I put thermal paste behind the LED board and on the pill threads to help dissipate heat better.
Testing it from a cold start w/ fresh battery, just sitting out, the head of the light will get too hot after about 30 sec. This is due to the whole light and battery absorbing heat.
From a warm start (ie going from med to high) it will get too hot at around 10-15 sec.
While gripping the light during use I can probably go for over a minute on high due to my hand absorbing heat. My driver doesn’t have a thermal stepdown so I have to be careful when running on high.
So, yes it can heat up fast with a fresh battery but keep in mind that IMR14500 batteries are only 600-700 mah. They won’t last long at 6 amps (6 minutes).
After a minute of use the amps and volts drop and you will be able to get longer run times on high.
I normally only use the light on the 2 lowest modes, say when reading in the dark, walking down a trail or rummaging through my car at night.
The high mode is only for short bursts (5-10 sec) outdoors for route finding and the wow factor.
I wouldn’t recommend this setup if you are looking to get 1800 lumen constantly. Your C8A driver will work but don’t rely on the 3 minute step-down, by then your light might be melted :).
Also, the hot spot of the beam is wider than the factory LED due size. And with this particular reflector there is some tint shift going from the hot spot to the spill area (not sure why though).