I can't say anything on the P+18650, but the P+500 works pretty well with the kick. The cap screws almost all the way down before you feel some resistance, but the last turn or so there is resistance to get it to screw down all the way. This is with one thin O ring under the battery and no washers under the negative screw post.
Performance wise, when I have it set to 8 watts, it literally blows any other device i have out of the water, including my Provari. I don't know why, but I get ridiculous clouds off that setup using a 3 ohm carto in a carto tank. Battery life wise, I only get about 3-4 hours tops out of the 18350. I do get some cutting out here and there far before the battery life has diminished, and it is not the kick's pulsing low battery indicator. Not sure why, but it hasn't been so much as to be an issue for me. I probably just need to tighten the negative screw post, and I am sure a bit of noalox on the threads on the bottom and top caps wouldn't hurt either. Other than the battery life, this is my favorite setup.
Performance wise, when I have it set to 8 watts, it literally blows any other device i have out of the water, including my Provari. I don't know why, but I get ridiculous clouds off that setup using a 3 ohm carto in a carto tank. Battery life wise, I only get about 3-4 hours tops out of the 18350. I do get some cutting out here and there far before the battery life has diminished, and it is not the kick's pulsing low battery indicator. Not sure why, but it hasn't been so much as to be an issue for me. I probably just need to tighten the negative screw post, and I am sure a bit of noalox on the threads on the bottom and top caps wouldn't hurt either. Other than the battery life, this is my favorite setup.