Another question to answer is how do 2 hot ends work on 1 toolhead, seeing as how time-consuming switching can be on other dual extrusion printers. Initially we thought, why not lift the toolhead up and bump it against a level and there your hot end goes. That is untill we were appalled by the thudding sound it makes every time one hot end needs to be switched to the other.
So the classy and efficient way to do it, we decided, is to switch with a motor. When your g-code tells the motor it's time to change the hot end, the motor will ask the linear rail to do the heavy lifting. Then the hot end gets changed, and the printing continues. This is done within 3 seconds, with a repeatability of 0.012 mm.