Watch out on the RK05, the power fail battery seems to still unload the heads on power fail even if that switch is off. If your finger is in the way the head positioner will win. Never put your finger/tools where unexpeced motion can get it (insert all the other obvious warning here). Also if you flip the switch back on when the heads are loaded the servo can get confused and go full steam ahead to the end of travel. This didn't seem to harm anything but did make me jump. A quick snap of the switch may help prevent this but I didn't try to verify.