I have a BLF A6 flashlight that I sometimes use with the short, 1x18350 battery tube. I'm fueling that with a KeepPower INR18350 battery. It works great. I do not have any testing equipment, but based on the reports of others, I expect I am getting over 900 lumens. There is no problem supplying the higher current used by the A6.
I considered getting a similar 16340, INR or IMR battery for the S1, but rejected the idea. The S1 does not have any low-voltage cutoff or warning, so my choice was to run it on a protected battery.