Previously, we had the ability to create and use Custom EventIDs in this range:

// Third parties can use custom events in this range to communicate between 3D VC's and 2D C++ gauges.
#define THIRD_PARTY_EVENT_ID_MIN          0x00011000
#define THIRD_PARTY_EVENT_ID_MAX          0x0001FFFF

I've notice that this no longer seems to work:

    <MouseRect>
      <Cursor>Hand</Cursor>
      <MouseFlags>LeftSingle</MouseFlags>
      <EventID>0x11009</EventID>
    </MouseRect>

However, this does work (assuming we have an event handler)

    <MouseRect>
      <Cursor>Hand</Cursor>
      <MouseFlags>LeftSingle</MouseFlags>
      <CallbackCode>
        (M:Event) 'LeftSingle'  scmp 0 == if{ 0x11009 (>L:EVENT, bool) }
      </CallbackCode>
    </MouseRect>

Is there something in Prepar3D v2 that is failing to recognize these via the <EventID> tokens?

Wouldn't it be better to ask L-M??

I already did just that, Ed. Still no answer though. In any case, I thought I'd post the results here in case anyone else has been wondering why the <EventID> method apparently isn't working, and a viable workaround.