That is actually smaller than my gap but mine is at the switch end, if you want to change where your gap is then take the switch off tighten the batt tube and then screw on the switch and your gap will be there.
He said you could trim the insulator in the switch to make it flush but that could cause your batts to rattle if you choose not to use the kick at some point.
He is coming out with an 18650 + kick tube and I am hoping that it will be designed so that everything fits flush, especially since it will be made specifically for the batt and kick together with no other option. Personally I prefer the AW IMR batts ans since Kick has a disclaimer to only use those, when Faceless does the 18650 kick tube it should only be designed to work with that configuration.