Yes, there are. Some time ago Simon has switched from triangular to trapezoidal threads. This has been discussed on this forum on several occasions
Hmm that’s annoying! I wanted to swap the heads but the newer light came with square threads and the other one I have on order is probably the same. Oh well, more incentive to build a new one xD
If you get an S2+ with a driver retaining ring, you can easily grind down the inside of the ring to make room for the components on the battery side.
Here’s an example of one of mine:
Are the trapezoid hosts available for sale anywhere?
Maybe you can ask Simon if he still has them. There are different stores selling S2+ lights, but I’d guess it would be a lottery trying to find a specific one. So, maybe the source is the best solution 
I thought the difference was
The Older S2 Grey or Black They had the bigger pill Slightly longer head
The Newer S2+ All colors ( labeled S2+ on the tube ) shorter pill
Almost correct
The older S2 has a slightly longer head, has a long reflector and a short pill (left)
The newer S2+ (that we know now), has a short reflector and a longer pill (right)
The left combo fits the S2+, but the right combo does not fit the S2.
The inside thread in the S2 head does not go “down” as far as the S2+ thread.
Simon apparently doesn’t have any hosts with the trapezoid threads.
Is there any way to identify the ones with the old threads other than by the threads themselves?
Oh well I tried —- I’ve only built 20-30 S2s—- You turn 60 and everything goes to S—T
After seeing your picture I started to wonder, if you could built S2+ with S2 pill and S2+ reflector. Then it might be possibe to use 18500 tube with 18650 battery. Kind of full size shorty S2+.
With a TIR lens, and possibly needing to replace the driver spring with a brass nubbin, you can stick an 18500 in an S2+ with a shorty tube.
Well, maybe I someday try to build 18650 using S2+ with Jaxman 18500 tube and S2 pill. Kaidomain has those pills separately for sale if I remember correctly.
I wish Jaxman still sold hosts. I’ve thought about buying an E2L, but I don’t think dealing with the thermal glue would be worth it.
I have heard that said many times. I am glad I am nowhere close to finding out!
Nope, you can’t!
The logic is precisely inverse to what you say! If you use the S2 reflector/pill in a S2+ (which is already shorter than the S2) you will eventually reduce the space you already have for the 18650 battery with and 18650 tube.
The mod you can do to have that configuration is to turn the S2+ into a triple, by using the S2 pill in a S2+ .
I’ve done that mod inspired in some other people’s mod, too.
You have mine here, and you have this thread of g_damian, and this CRX thread, and this Firelight2 thread, and even some comfychair .
See those and you’ll be able to fit an 18650 into an S2+ with an 18500 tube
I thought about using S2 pill and S2+ reflector. Isn’t the total lenght then less than using standard S2+ pill and reflector combo?
Sorry, I misread your post! 
Yes, indeed, the S2+ reflector and the S2 pill make it shorter! Still, to make an 18650 fit there, it is virtually impossible.
Below there is a photo showing how much an 18650 stands out the tailcap+18500 tube. Allo a margin of 4-5mm of compression there, due to the spring on the switch side.
On the side you see the S2 pill w/ S2+ reflector and the pill with optics of a triple. Even with that margin, you wouldn’t be able to fit it.
Unless the driver and the switch base were almost “flat”, and still, I have my doubts that you could fit an 18650 there.
Oh, and please note that due to the differences in threads, not all the S2 pills fit S2+ heads!
So it’s going to be hard. That sparks my interest. Just ordered host and 18500 tube. 
Ahah, that’s the spirit
Let is know what you achieve when you do it !
But don’t be too hopefull 