I recently acquired a Fenix TK75 (2015) and I have plans to mod it. I’m definitely putting dedomed XM-L2 U4 1As in it and was going to do a resistor mod but I’d like more output than a resistor mod will give me. I’ve read several different threads about different mods and it seems that the mods that output benefits the most from are those where the driver is replaced. The only driver that seems simple to put in place, simple for me any way, is this one. However, I do not possess the necessary equipment of skills to reflow smd chips to a driver. I’ve always purchased mine already built. I’d be more than happy to pay for the labor put into building it…as well as the parts of course. 
The driver you chose cannot be used in Tk75. You will need a fet driver with ldo. You have a 8.4v source which powers 2 xmls in series.
On the same page of the link that I posted above, in the first post it says:
So you’re telling me that this driver with the components mentioned in that post will not work with a TK75? I understand that the battery carrier has to be configured differently…I’m just looking for a solution for max output.
Reflowing is not magic, you need
a heat source like heat gun, stove ect.
Solder paste
Tweezers
It’s magic to me when it comes to tiny parts, lol.
DJ , TK 75 in stock form is almost on the edge of its capabilities of dissipation of the heat . At around 4.2-4.5 Amps per led you'll get up to 4500 lumens (with the original driver , modded...). Is what I did to mine , dedomed leds, lapped surfaces , good quality silver thermal paste, tightened MPCB , resistor mod up to the point where you can lose the UI .., I even mod the carrier by removing the two diodes inside and replacing its with copper straps !
The results are good , but not great, but I'm glad that turned out like this because the heat became an issue , you can feel the difference within a minute ! Maybe the heat path are better now ,but using it inside is no longer an option for long period of time !!!
The idea is to find the best compromise , in order to have a reliable light and not a hot rod for a minute or two ...
“On the edge of its capabilities” I guess this phrase is kind of relative here.
You are right .., was JUST a personal opinion... I sensitive on my hands !!!
^
cera@1967 is right about the light being near max on thermal, but must of us use Turbo for just a few moments and then go back down to a lower mode.
Sounds like a great plan djburkes. 4S cells bucked down to 3S emitters will allow you to drive the emitters as hard as you wish. I drove mine stock emitters to 7 amps. I didn't dedome for throw though.
Given that there is a contact plate and some space above it, you can probably fit a buck driver in there. My build thread may make it look harder than it needs to be because I added a third switch (a clickie for lockout).
I’m looking to get somewhere close to 6,000 lumens out of it on turbo. I’d rather leave the stock driver alone and stick a different one in but if I have to do a resistor mod I will. It puts out a great beam as it is…I just like to get everything out of a light that I can. I’m just fascinated by the amount of light a little ole led can emit.
I feel like an idiot asking this but how do you remove the reflector on a Fenix TK75 2015? I’ve removed the bezel, lens, and o-ring but the reflector will not budge.
Nevermind…gave Vinh a shout…now it’s out!
After swapping emitters for dedomed XM-L2 U4 1As last night…I don’t even feel like a bump in current is required. She puts out a nice beam.