Nice mod! Looking forward to the beamshots.
The 12V XHP70 should be at maximum output at 6A, if cooled well, like you do in this mod. But I'm sure it survives a current that is much higher, 8A should be no problem (the XHP70 that I tested in 6V set-up survived 15A with no noticable damage, see OL's XHP70 thread, post #575).
nice work! 
Gotta love the sleepers!
Love it!
So, other than the XHP70 and base, everything you used was just stuff already laying around the house. Since you could always reused the emitter/base in another light someday, this light really cost you nothing other than some hobby time. Now that is budget at it's best.
Guess you could put a couple small balloons in the light to keep the floating functionality. Just don't test it while taking a bath. 
beamshots? i’m drooling…
I see you’re on the East Coast too.
Gotta wait for the dark
Mean while I am bench testing and working on an FET switch. No way that wimpy stock switch is gonna handle 6A!
At 12V, that’s 72 watts
lol - I wondered about the switch :)
Up until now, I have only been bench testing this light. Running it while not assembled and not using the stock switch. The original LED in series with the 15 ohms of resistors probably only drew in the neighborhood of 200 mA. That stock switch probably couldn’t handle 6A, even once. So I built an “FET switch” based on this circuit
This circuit with a low power LED could be used to test various FET’s in a Go-No Go situation. I eliminated the 1K resistor because in this circuit it is a current limiting resistor to power what would have been an indicator LED to signal on and off during the test of the LED. The 2 resistors I had and for the FET I used an automotive FET salvaged from a drill pack. In this case it came from a Ridgid pack, part IRF1404z. It can handle 75A so 6A is a piece of cake! Even with no heat sinking. The stock switch is a push on, push off. Push once and release and the switch stays on. Press again and switches off. Perfect for this application. Now instead of having to pass 6A, it only see a few milliamps.
Nothing fancy, I soldered the 3 components directly to the traces on the back side of the reflector.
At the top of the picture there are 2 connectors that make contact with the switch mounted in the forward top of the light. They connect when the reflector is screwed into the light.
All there is to do now is wait for darkness
Sweet. I need to keep that FET switch circuit in mind.
I updated the OP with beam shots and a short video
Thanks Ronin42, so far, you are the only one to respond after I posted beam shots, 
To answer your questions, firstly think of the FET as a valve. In fact the names of the pins are “Drain”, “Source” and “Gate”. A water valve, a “Gate” valve, would have a place for the water to enter (the source) a place for the water to exit (the Drain) and a shut off (the Gate). Open the Gate and the water flows, close the Gate and the water stops. Simple as that.
In the circuit for the FET the Gate is closed when it is low (negative) and open when it is high (positive).
In this schematic, when the switch is open, the gate is low meaning that it is negative. It is connected to negative through the 68K resistor. Close the switch and it becomes high and opens up. Even though the 68K resistor still connects it to negative, the much lower 100 ohm resistor opens it up.
Picture of a Gate Valve
Notice in the diagram they use the terms Gate Up (high) when it is open and Gate Down (low) when it is closed.
As to the tint of the XHP-70, it is definitely warmer than the SRK. When I ordered, it was supposed to be 5000K and I think that is about right. The SRK looks COLD in comparison.
And to answer your third question, I am sure the LED would blow up with 5S. I purposely used weak cells just to be safe. Better cells would not drop a lot less than as much as 2 volts.
BTW, the Sleep Light puts out a lot of freaking light. Compare it to the cars passing by. (no one would have had their high beams on though)
That's a heck of a lot of light coming out of a plastic light. Must feel a little funny holding a plastic light pumping out that many lumens. How does it feel in comparison to the SRK weight wise?
I really like that, thanks for sharing.
LOL, it vibrates!
That poor 12V fan is spinning like crazy running on 16V
It’s a flooder though for sure. Like you pointed out in another thread the reflector is shaped so that most of the lumens just spill out.
I wouldn't think the fan needs to spin very fast to effectively cool that heat sink. You planning on putting a resistor in series with the fan or something when you go to the next level of cells?
Looking forward to hearing how your XHP70 handles 4 health cells.
HAHAHA, that is some awesome sleeper man, excellent work!!!
GB anyone? 
Grtz
Nico
That’s pretty sweet! Thought about resistor modding the fan to get the voltage lower?
Yes I will do, AHEM, “the resistor mod”
I’m gonna have to open her up too as pommie pointed out. It’s gotta breathe, it gets hot in there!
Heck even a “Sleeper Car” might have a hood scoop, right?
I’ll do it discreetly. 0:)
dchomak thank you so much…
Excellent, Excellent, Excellent
Wow your explanation is one anyone can follow (if I can). I had to look at it for a while but now I get how you are using the FET (look at me throwing big words around) to be the actual switch. I guess with all the resistors it is not open and closed but more and less closed.
Sorry lazy brain, yes I did not take the time to check the voltages at 4s you are already over the 12v for the emitter. Better to go with 4s2p heck, you have the room.