Samsung 20S would be your best bet. Absolute monster.
For a 4P setup, you need to go all out.
Since you are very skilled, put dual BeCu springs in the Q8 and bypass that array for absolute maximum conductivity 
You want as low of a resistance as possible, and a bypassed dual BeCu spring array will do the job 
Are the 20S better than the 25S?
Already have the large springs on the board with 22 ga (20ga? forget) bypasses. 
Edit: Forgot what I’d done on the bottom end, I simply pulled the tube and tail assembly from my XP-L2 build and put the large spring with bypass on the XP-L2 build. So the new one will have dual springs on a copper plate.
Yes, it is the best 18650 cell in terms of power output:
https://www.e-cigarette-forum.com/threads/bench-test-results-samsung-20s-18650-hardest-hitting-18650-right-now-beats-hb6-and-vtc6a.864225/
The Samsung 25S actually bests the Sony VTC5A by a wee bit, and at 2500mAh it would have quite the leg up on a 20S. 4 in parallel would mean the 20S would need a whole 5th cell to keep up.
Edit: According the HKJ, the Samsung 25S at 25 and 30 Amps really hammers the Sony VTC5A, which I thought was the best cell out there in the 18650 class. Appears I was wrong. So, I will need to get some Samsung 25S ordered. (more of them I should say.)
Nice mods guys. This forum almost needs a name change that includes black magic. 
Small Mod. I bought a cheap charger on Aliepress. I found that it is suitable for long batteries 21700. Including super long with protection to Rofis MR30 and Wuben A21. I removed the electronics, added the furniture angles as contacts. He slightly trimmed the charger’s contact. Now I have the perfect reduction on the 21700 batteries in my OPUS charger.
Nice mod. I’ll be copying it myself soon enough
Modded my copper Convoy S2+. Actually, re-lego-ed it.
What stayed: all copper parts with O-rings, The XP-L emitter, the lens and the opaque tailcap rubber.
What came in: long smooth reflector and short pill from a Convoy S2, X6/X5 driver and lighted tailswitch,
and a nylon M8 washer I got from a local DIY-store.
I got: a reasonably throwy almost neutral white tube light with a nice hotspot (a bit greenish in the very centre).
And while I suspect my LX1010B luxmeter consistently shows values that are too low, the output = 19 kCd.
Sounds very nice Henk! The shallow reflector of the S2+ has never been my preference.
A quick and dirty mod tonight. I blued my AT40. Unfortunately I held the torch over the tail for extra long (that was where I started) and the colour went from blue back to pale. I let it cool and tried again but it just didn’t turn out. It’s blue inside the tail. Maybe if I sanded it back and tried again it might work…???
I am just modded by you folks 
Great great mods, all different, all cool ! Great work, mates :face_with_monocle:
Finished up the red utorch s1 mini for my wife.
Beam profile was exactly what I hoped for (why I used the SSL-80 version of Olson) but had pretty bad artifacts / rings on the wall so a layer of DC-fix on the inside of the lens fixed that right up
What happened to the heart positive contact ?
I thought I would be able to cut / file some 3mm thick Cu sheet (to replace the stock button) but that didn’t happen 
I wasn’t able to shape the thick Cu sheet well enough by hand (diamond files and shears) so then I thought I’d just make 3 1mm hearts cause I can shape the thinner stuff well but I couldn’t stack 3 tiny 1mm thick hearts and get them to solder together and solder to the PCB clean enough to feel good about it…
Instead I just reused the factory 3mm x 5mm round button and gave her one of the blank PCB’s. The pad is a heart, just the button didn’t happen.
I tried a solder blob first, you can pile on about 1-1.5mm of solder and have it retain the perfect heart shape but it wasn’t enough height to work
Sometimes the box needs to be shredded and tossed aside… why didn’t you simply solder the brass contact button to the top of the cell, leave the heart pad in place and let it show clearly at every cell charge?
You could also have went with the solder blobbed heart, solder blobbed the top of the cell to meet it. Seems a shame to have gone to all that trouble to make the heart pad only to obliterate it in the end.
Convoy BD06. Quad Luxeon V. LD-B4 9A driver. Blue GITD tape.
I was having issues with my Convoy S2+ (with biscotti) recently. It was switching modes or not turning on. I thought that maybe the switch or connection was bad.
I bought a new soldering iron (TS80), but have never used one, so have been hesitant to try it. This was a perfect excuse to practice by replacing a spring and seeing if I can fix it. I replaced the original spring with a carbobronze spring. The soldering job was horrible, but it held. I may redo it, eventually. I removed the front ring holding in the driver in order to replace that spring as well and noticed it was loose. I tightened it back up and it solved my issue. I am going to use it for a few days before messing with the spring on the driver, but it was my first mod/repair so I wanted to share.
Yep, I had a similar issue with a Sofirn SP/SF/whatever light æons ago. Thought it was a wonky switch, too. Saw that the driver’s retaining ring was loose, snugged it up, worked perfectly ever since.
@Calaveras, you need a flat tip to do most soldering jobs.
Here is one which will work well:
A bit expensive, but totally worth it.
