I was playing around with an S2+ host using a Nanjg 105C AMC7135 x 8 driver with an SST-20 2700K installed. It didn't work but after a minute the pill got so hot that I burned my finger a bit. I then tried a CF FX-17A driver and it was okay, Is it the Nanjg or maybe a short somewhere? I didn't use the retaining because there was no room.
Nanjg 105C
The retaining ring is used for pressing the driver into the pill.
The ring sits on the spring side of the driver, the contact is on the “in”side of the driver.
The driver has to make contact with the pill in order to function. Always.
That’s why we always ask first: have you checked if the retaining ring is screwed in properly?
A regular Nanjg driver maximally has room for 8 regulators. The well known AMC7135.
As a rule the first 4 regulators are placed on the inside of the driver. The others on the outside.
If there is more than 4*AMC7135 regulators, like 6*AMC7135 or 8*AMC7135,
the AMC7135 block’s make it impossible for the retaining ring to get into the threads of the pill.
You have noticed that already.
The quick and easy solution is to solder the driver board into the pill.
Almost always good contact, leading to a good flow of electricity and of heat.
Minus point: because of capillary properties of the flowing soldering paste quite hard to remove.
There is a more elaborate workaround.
Grind out the inside (NOT the threads) of your retaining ring.
That way the ring (cupping the AMC7135’s) can reach the threads on the inside of the pill.
This is a LINK to a thread were (also) several other solutions are proposed.
Okay my bad 
Driver tripe and old thread. 
I think easiest way for me is the solder way. Gonna give err tonight and see how it goes.
” It didn’t work but after a minute the pill got so hot that I burned my finger a bit.”
It didn’t work meaning there was no light emitted? If there was no light and the driver got hot then there was something else wrong.
Well yeah I was thinking the driver maybe? Like too much juice or something.
Okay this is what I did.
-Solder correct polarity to SST20 mcpcb.
-Applied thermal glue to mcpcb
-Center driver in pill without retaining ring
-Insert batt and then tube making sure driver is centered and straight inside pill.
Then I clicked and no light but around 30secs later the pill actually burns my finger a bit. I’m thinking either a short or the driver compatibility with led maybe??
On the top side of that nanjg driver the positive solder point is very close to the outside of the driver. I wonder if the driver was a little crooked (since it was not held properly in place) and the plus shorted with the pill. This would essentially short the battery.
Yes I will go over tonight and chk contacts points closer. I’m thinking it’s a small short somewhere like you mentioned about the crookedness. Good thing I didn’t leave the batt inside! Was putting it together just before bed so probably missed something. 
UPDATE
It turned out without the retaining ring, the driver was not making contact with the pill. After soldering the driver a bit to the pill, it works fine now! Thanks again for the heads up all. 
Glad it’s okay now. Most of us have been there before, once or twice. Or more 