That is one beautiful light! Great job with the copper spacer! Just wondering why connect the aux led direct to the battery? What is the issue with the original connection config?
Gorgeous Light ” Skylight ” Great build 
Its hard to believe that was even possible to do. 
So much talent in this years competition, Wow 
Thank you, MascaratumB. Yes, it is an awesome flashlight if you hold the whole 1042g in your hand and it lights up everything with a huge smooth hotspot. :sunglasses:
I needed something variable and thin and that was where the coins came to my mind. I’m glad I tried it before because if the copper spacer is not high enough the leds are not in the optic like they should be. First I wanted to cut 24mm but with the coins staples I found out that I actually needed 29-30mm.
Thank you, YogibearAl. That copper spacer was certainly not easy to build with only a hand saw and some filing.
In the first configuration the aux leds did not light up. The board is designed for 8.4V. Only the next version (v3.1) can be MCU-controlled and turned off if desired. This is the first version and the simpliest way to drive aux leds is to just connect them to the battery with the right resistors and parts on the board.
Well, at least I have an MCU-controlled lighted switch. After some experimenting you will leave the aux leds on one brightness anyway and if a flashlight has aux leds where is the fun in turning them off?
With some more electronic knowledge you could drive the board over a small FET like Lexel told me but that is too complicated to realize for me.
Thank you, CNCman. 
Once you have that copper spacer the rest is not too difficult as the L6 is like it has been made for this MF01S optics and MCPCB.
I could have done also a simple mod but it always needs to be a bit challenging, right? You need to test your abilities and maybe try some new things.
Some more info about the flashlight
The Matainvoy ML18S weighs 862g empty and 1042g with batteries. To compare, the Astrolux MF01S weighs 702g with batteries and the Convoy L6 582g empty and 774g with batteries. So it is heavier when empty than each of the other two with batteries.
The weight is concentrated on the head but I don’t consider that a problem as you will hold the flashlight anyway at the head where the switch is and the long battery gives some balance. It might be too heavy to carry around for longer use. The copper spacer I have added to the head weighs 310g with the thick wires and is maybe 280g solid copper.
The thermal transfer works well. After maybe 20s on turbo you can feel the head spreading from the bottom and the top of the head where the copper contacts the aluminium body. The whole head heats up slowly and evenly especially when all the copper was cold. On the other hand it also stays warm for a few minutes after a few turbo bursts.
Towards the end of my video you will find a tailcap current measurement. The clamp meter has to adjust the scale to the next level when you turn on the Turbo with a double click. I have never seen this on any of my flashlights before! With two fully charged golden Golisi 26650 4300mAh, capable of 30-35A discharge and as mighty as a 30T, the current is 17.6A on highest ramp and 29.2A on turbo. That would be around 3A per led and if you use four 30Q’s in a MF01S with 15A discharge the leds wouldn’t get much more. Of course the runtime is reduced but after a few turbo the batteries were still at 3.9V. My estimate would be around 15 000 lumens for the ML18S.
I had both the ML18S and the MF01S together on turbo with full batteries and I can tell you that the MF01S heats up faster. When you don’t feel the heat on the ML18S the MF01S is already warm at the head. I assume that my flashlight would run a little longer on turbo while heating up the 300g copper spacer but it will step down, considering also the voltage sag on the two 26650 at 30A.
Beam and tint
The tint is a bit green at low levels but without a direct comparison you won’t notice it. The MF01S with 4000K SST20’s is slightly rosier and warmer. The tint mixing of 4000K and 5000K LH351D’s gives you around 4500K.
The beam is wide and uniform. It has a big hotspot, maybe twice as big as an MF01S as you can see in my whitewall beamshots. This big smooth hotspot almost reminds me of a zoomie and as I like zoomies I love the big, floody beam. The throw is not bad and it reaches out 150m easily. It is the floody sister of the MF01S and where the MF01S throws further with a smaller hotspot, the ML18S impresses with a huge and blindingly bright big hotspot with not bad reach.
Most challeging task: Cutting the copper and leveling the copper spacer to fit well
Easiest task: Changing the switch cover from black to transparent 
Most satisfying thing: Seeing the main leds and aux leds light up for the first time
Some things I have learned: Soldering with low temp 138°C solder, using a hot plate, soldering a 300g copper spacer, connecting aux leds and maybe some more things I forgot to mention.
The Matainvoy ML18S will always be honored by me as my first OL-contest build and hope fully not the last.
I would like to round off this thread with some acknowledgements.
Thank you, Lexel, for your great drivers and custom aux led boards. Thanks for your fast answers and useful explanation. The ML18S would not have been quite as great without an Anduril driver and an aux leds Board from you.
Thank you, AEDe, for the LH351D’s that I got from your group buy. It was perfect that I could get some in 4000K as well. The LH351D’s are astonishing under an MF01S optic and give the ML18S a really nice beam.
Thank you, BlueSwordM, for your great BeCu springs. They do an excellent job in the ML18S and allow it to handle the 30A current with ease. Thanks also for the FD2 SST20’s that would have taken the 4000K place in the tint mixing if I wouldn’t have been able to buy 4000K LH351D in time.
Simon Mao from Convoy deserves a mention as well because he designed the Convoy L6 which was my first over 1000 lumen flashlight and is still one of the nicest hosts I have. I just had to have another one in brown even though it was not from Convoy but from Wainlight.
And finally, many thanks to all the BLF members for organizing the OL-contest, for encouraging the participants and for the nice welcome every one who joins gets.
Many thanks to everyone who followed my thread and left some kind and encouraging comments but also to everyone who read my comments and looked at the pictures. I felt like being a part of BLF more than ever before. 
I’m glad I have joined the 7th BLF Old lumens contest and I am really pleased about the outcome, my Matainvoy ML18S. 
Well done on completing your build :THUMBS-UP:
Awesome video of a really great mod. Thank you, I really enjoyed watching it. And, to my surprise, my wife watched with me.
Congrats for realizing that one, very good job and great result
Lots of bits and pieces disappeared into that light Skylight. Not sure how you managed to fit it all it but nice work.
Thank you, Agro. Great that you liked the video. I supposed it would be interesting only for modders and flashaholics but it is nice to hear that also non-flashaholics can watch it. All the one, two or three minutes clips cut together turned out better than I expected. This is actually my first Youtube video. :partying_face:
Thank you for organising the BLF OL-contest. 
It was great to be a part of it and it lets you feel the spirit of BLF. So many people are watching, write nice comments and that is very motivating.
Thank you, man of light. :sunglasses: This mod could be nice for others to try as well. I really like the result and I’m relieved that I managed to complete it all.
Thank you, MRsDNF. Yes, you are right, lots of copper, lots of cables and lots of leds. :smiling_imp: I was lucky that the driver cavity on the L6 is rather big and you can fit in all those cables.
Skylight, I maybe missed something. It looks like the driver is a FET driver, not buck. Is the MCPCB wired for 2S9P configuration of the 18 LEDs (some sort of 6V board)?
Yes, it is a 2S FET driver. The MCPCB is 2S9P and can be directly used with 6V. I got it from the Mateminco store on Aliexpress.
It is the new MCPCB that they are using in the Mateminco MT18S or Astrolux MF01S. The 6V board is designed by Lexel as it is written on the board. The old version, the Astrolux MF01 or Mateminco MT18, used the other board with 6S and boost driver.
Banggood is still selling the old MCPCB with Nichia 219C but the Mateminco store has got the new version that is 2S stock and much more convenient than the cable mod.
Cool, thanks - I’d forgotten Astrolux did all their four-cell carriers as 2S2P, and was thinking of it in my head as a 4P light.
Amazing build! Congrats on the win!