The 215m controller won't control a 315m head correctly. There is more temperature control on the 315 head that keeps it SLM and this requires the correct 315m controller... Allegedly
Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001