As long as it is connected towards the negative side it should turn on. i do not see why it has to
connect directly. see after it is initially started, the inductor becomes the power supply, ie the central point of potential which is releasing from the inductor.
it is my understanding that as long as one side is pointing to pos and the other to neg it should turn on. anything below the drain is considered negative and anything above the source is considered positive correct.
the other circuit i have has an n channel in place of the opto which is logic level.
granted, these circuits have not been fully tested just yet so obviously testing dictates final circuit.