Can't use DnD events with Mouse events

I'm trying to build a data mapping app and running into the event issues introduced with DnD. I would like to draw a "rubberbanding" line between "ports". When over the target port, I'd like to Drop some info onto it. The attached code (with commented _port.setOnDragDetected method) does the rubberbanding as described (the ports are enlarged for demonstration). If that code block is uncommented, the Drop works as I need it to but events are no longer delivered for the line drawing. Problem is, both functions are required.