I don't think it is possible to charge an X2 using a 65/78mm adapter for several reasons. There is probably a diode which will prevent reverse current, charge current, from flowing into the battery from the cartomizer end. I believe that connection is also electrically protected from over current and damage to that protection circutry could result if charging is attempted from that end. The output of a 65/78mm adapter is probably at least 100ma short of the necessary output current to charge an X2 in anything resembling a reasonable time frame. To add to all of that, I don't think SI would warranty an X2 that had been charged, or possibly damaged, using this method. I would suggest sticking to the mini USB connection only for charging or pass through use.
Just my opinion, worth what you're paying for it, your results and mileage may vary, no warranty or guaranty is expressed or implied.