I just got 1 today and it still has the red stuff on it. I have a 2nd one on the way, maybe it will be different.
I guess it varies. My replacement also had different color switch wires.
Both my hosts have different wire colors they must just use random wires. The red stuff is surely just to make the switch connection more durable.
See the green line.
If the drawing (from the first post of this thread) really resembles the C8F, then you can take away some of the threading. Just make sure you have
- enough threading on the retaining ring left to hold the ring under pressure and
- enough space on the lower side of the ring to fit on the bare copper on the driver.
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Pretty sure he means this (Pic courtesy of ImA4Wheelr). This would be the “underside” of the ring, notice, no holes for pliers cause it’s upside down.
No, pretty sure he doesn’t 
What I mean is filing the threading of the retaining ring.
Underside, yes, but from the outside, to remove some threading so you can turn the ring a bit more.
Your picture, contactcr, shows filing down the inside of the retaining ring. You do that when the ring collides with parts on the spring side of the driver. This wouldn’t be the case here with the C8F.
Wouldn’t it be easier to just put a few solder blobs on the outside of the driver? I built mine with a 1.2mm thick 20mm FET+1 and had no issue but I guess YMMV. The ring is ridiculously thick so i’ll leave up the pic even though it isn’t what you meant.
I did file down a little of the lower threads, but it had no effect on where the ring stopped rotating. Very strange. I may have to look at it closer.
Unfortunately I don’t have the 21700-C8F yet, so I can’t check myself.
I did this kind of filing several times with brass-pills (before the pill-less design took over) and it worked well to get the pill in deeper.
Of course you can do a comfy-style solder addon to the driver. Preferably the component side, as solder does not hold pressure well, especially not with a shearing force like from a retaining ring.
Btw, comfychair used a drill press to ‘mill’ these solder blobs flat. That was a classic.
Hey Sofirn next let give us C8F 26650 and the single emitter throwy version either 21700/26650 .
Why do you want 26650 when 21700 has almost the same performance but more compact?
You get longer run times, plus it feels better in the hand. The smaller 21700 is a bit awkward for me.
Then there is the SP33.
I talked Sofirn again. They told me that talk with the engineer and will think about the songle led 21700 version. I said that make it like C8F so same double switch just change the front end to single led.
Like ZozzV6 said, the old SP33 was a single emitter 26650 light. I’m not sure why they changed it to xhp50.2 with boost driver. Maybe low sales? It might have been better to have 2 seperate models.
That good I like the 2 switch with forward click tail of 21700 C8F , hope for bigger head (55-60 mm.) with XHP35 for better throw and please make the light switch to stay on as locator .
Now your asking for a completely different light.
You want Sofirn to make a light like the thrunite catapult v6 or lumintop odl20c, but with 2 switches?
Yes that I mean Jason but with Sofirn price. 
I recently received 2 C8F 21700 hosts, along with a driver kindly sent by Sofirn, and today I found the time to assemble 1.
I used 2 pieces of 16AWG wire (about 4-5cm each), 3x XP-L2 V4 4500k 80CRI 3-step, and the Sofirn driver.
And I was really amazed by the result, I measured 17.8A max at the tailcap, with a 30T @ 4.2V
THANKS Sofirn.
That will be just under 5000 on-LED lumens, right? 
Anyone know if the 21700 host will show back up in aliexpress store?