I regularly print with carbon fiber and glass reinforced Nylon and have upgraded all of my other printers to the E3D Nozzle X. While the J1 is designed to work with MK8 nozzles, E3D V6 nozzles work great with a slight adjustment. Overall nozzle lengths are within 0.5mm, but the threaded section is 2.5mm longer on the V6 nozzle. To compensate for this difference, I just unscrewed the heater block from the heat break by a couple turns. The E3D V6 nozzle then screws in just as it would on an E3D hotend.
The net result of this change is the heater block now sits about 2mm closer to the tip of the nozzle.
All calibration functions still worked perfectly after this change and print quality is still great.