The BIGGEST issue I have with the Gemini is the 510 pin as well...
One it's NOT adjustable, and it is WAY TOO LONG! Good luck using it with any Joyetech/Wismec/eLEaf mods... Worked on my Cuboid, but wasn't flush, BUT I could tighten it so it wasn't loose. On the RX200, I had to leave it pretty loose, or else nothing but errors, no atomizer, bouning out of TC mode, etc...left it a bit loose worked fine. If I used a 510 heat sink, or spacer worked fine... The 510 pin on the Gemini is THE LONGEST of ANY RTA, RBA, etc.. Total from the base to the pin, 5.6mm!!!!
If you want to use this on a Joyetech/Wismec/eLEaf mod, use a 510 spacer, heat sink, neoprene washer, or something 25mm x .5mm to about 1mm thick! If you don't, expect problems, either immediately, or down the road...