The Quark Mini will put out 250+ lumens*** if you put an RCR in it. No need for an SST-50 upgrade. Don't blame us if the RCR explodes and destroys your hand. (That is why Joe Talmadge suggested IMR batteries which can handle the current. At least use an AW protected 16340.)
The problem as many others have mentioned is heat.
I have an Elektrolumens EDC-P7. The LED is in the same power class as the SST-50. It is 5.5" long, 1.5"Ø much bigger than a Quark Mini. It got too hot to hold in 5 minutes. I was on a 1+ hour hike. Luckily I had my 3C Mag with me.
I donated an L0D CE. I supplied a 10440 with it. The recipient decided the light with 10440 runs too hot and went back to a regular AAA.
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***The Preon has essentially the same LED and circuit as the Quark Mini. Running a 10440 in a Preon is very similar to using a 16340 (RCR) in a Mini.
Note a 10440 in a Preon is running at 4C, double the 2C safe limit of Li-on batteries. The 16340/RCR123A in a Mini is running at 2C or at the danger point. An AW IMR16340 is rated to be safe up to 8C so should be safer from over-current danger. But it does not have low voltage protection. The AW protected 16340 provides both over-current and low voltage protection.
Jay R got over 280 lumens with 3 different Preons with 10440.
https://www.candlepowerforums.com/posts/3387177&postcount=1
bigchelis got 326.2 and 327.7 initial lumens from 2 different Preons with 10440.
https://www.candlepowerforums.com/posts/3387389&postcount=3
You should get similar results running a RCR123A in a Mini.
Note how the heavy drain is affecting the batteries. bigchelis got 326.2 and 327.7 initial lumens but by the 3 minute mark is down to 222.3 and 218.5 lumens. While a 16340 has double the capacity of a 10440, you still won't be able to maintain the initial lumens for long.