How to open Quark or Fenix head?

I want to perform an emitter swap on my Quark S2. But before i destroy the Quark head, i wanted to practise opening it on the Fenix PD20 head, which seems to be built in a similar way.

The tips i have read so far:
-heat it up to soften the loktite
-use pliers + rubber band
-use strap wrench

So today i bought two strap wrenches and tried to open the head. But they started slipping without any indication of movement on the head. Then i preheated the head with a hot air gun, but the heat made the strap wrenches' rubber band even more slippery. Then i tried fixating the head in a vise (with those rubber bands for protection), and gripping the smooth part of the head with a pair of pliers, again with rubber band in between. It slipped. Tightening grip -> it slipped in the vise. Tightening vise -> it slipped again in the pliers' grip. I gripped so hard that the part with the screw threads is now deformed and the head doesn't fit onto the body anymore.

How the hell can i unscrew the head without damaging it? I'm running out of ideas...

i'd sya try the strap wrench on the quark. it is unlikly to damage it and you might find out that the Q opens easier. depending on how bad you think the heating is for it you could try that on the Q also. basically what i am saying is you might get lucky and the Q will open easily, it is worth a try

It also starts deforming before i can get enough grip... i tried without heating.

You need to leave the head on the body to keep it from getting out of round. I used 2 strap wrenches with a plumbing pipe wrench on one and adjustable pliers (channel locks) on the other side. My first one was easy but the second one must have had more locktite and needed heat.

Thanks! Leaving the head on the body helped. The head still deformed a little, but not permanently. Enough though to make the lens crack a little. But the lens is now replacable