....And while it is pretty much verboten in the tech/cave community, shoulder dumps are pretty common and seldom fail. ...
....Consequently, I'll take the position that you don't need an inflator elbow dump, but it is not a threat either and can make the process of dumping gas a little easier....
...Also, Scubapro normally has a right shoulder dump valve on their BCs. That is to allow simultaneous dumping with a pull cord on the BC, while breathing off an Air 2. One could argue that the right shoulder dump is another failure point high in the bladder or wing, but 30 years of successful operational use by tens of thousands of divers suggests it's really a total non-issue. ....
...It's not rocket science, but the arguments against tend to fall out on dogmatic lines rather than based on actual experience and objective reasoning of what makes sense in a particular configuration as a whole.