Best Way to Know a Single Point Output Has Gone Out

[Hooovahh]

I have an API where I'm talking to a device.  On closing of the device I want to put the device in a standby mode.  I'm controlling this using a Single Point Frame Out session with XNet.  So my issue is on close I need to set the value of the single point frame, then wait for the values to actually go out, then close the XNet session.

So my question is this.  What is the easiest way to know that a single point frame output session, has written the new value to the bus?  There is the Number of Values Pending property on the session.  But this seems to always read 0 on single point session types.

One method I thought of is to turn on the echo'ed frames, and then try to read them back.  This will likely add a decent amount of overhead for my API but could work.  Is there any other method to know that a frame written on a single point out, has gone out?  Thanks.