The J-head is also a groovemount system. My hope is that I can print a carriage to hold the two hot-ends that will make sure their cold ends descend the same distance below the carriage, then using plumbers tape tighten the hot-ends until they are the same depth, too.
Someone earlier asked if the J-heads could swap nozzles for different sizes as the person got more adept. The answer is yes, Brian offers nozzles from 0.35mm to 0.75mm at
http://www.hotends.comThe attached picture is with a 0.35mm nozzle.