Post a picture, it is a lot easier to give you an answer if we can see the problem. 16" is a long way off, maybe they gave you the wrong shaft with the PHD. Do you have a quick connect on the 3PH? That would set you back but not 16". I have a PHD and I have a Freedom hitch quick attach and I have moved the PHD through all its mounting points and never came close to running out of shaft.