mwmcbroom
Got a related question for you. Because of some effects I have loaded, after the song hits its final note, the sounds don't end there -- they taper off for a couple of measures before the tune becomes truly silent. So I was trying to figure out an easy way to extend the measures of the song. Well I didn't find an easy way but I did find a way. In the window to the left that shows "Clip Track ProCh", when "Clip" is selected, one of the data points indicates the length of that track. So I just edited that number to end it where I wanted, then copied this to all the other tracks. Including the audio track. After doing this, I got the sound I wanted at the end of the piece.
 
So is that the best way to do this or is there another, quicker way?  I was looking for a way to set an "end" flag, but nothing was jumping out at me as a way to do it. Knowing Sonar, though, the command is nested away somewhere where you gotta know where to look to find it.

 
Am I correct in understanding that you're talking about reverb/delay tails and such (audio FX on the soft synth tracks)?
 
If that's the case, you don't actually need to do anything - other than make sure "Tack FX" and/or "Bus FX" are enabled in the "Bounce to Track(s)" (or "Export Audio") dialog - SONAR should render audio to include all effect generated sounds, as well as the actual soft-synth notes. Just ran a test with some crazy delay applied to a kick track and the bounced audio ended up with 15 additional measures for the delay tail.
 
Do bear in mind, however, that the bounced audio is going to be the length of the selection on your timeline, so the tails might get cut off if you've only selected the full length of all your MIDI clips.
 
Because you want to mix down your whole project, the easiest way around it is to simply press Ctrl-A and Select All (all tracks, the whole timeline). Clicking on a track in the list to select it should also select the entire timeline. Alternatively, you can simply select the length of your song, plus however many extra measures you need, in the timeline directly.
 
If, for whatever reason, you need to put extra empty measures in one or more of the clips, the quickest way is to grab the end of it with the mouse and drag it out for however long you need.

mwmcbroom - if you're just using soft synths, don't even bother with bouncing, just freeze the synth.
This will create the audio track(s)  for you.
 
If you want to change the Midi, just unfreeze, tweak, and freeze again.

Thanks for your suggestions. I've just been muddling along, changing the endings of each track in the Clip box. It works well enough.
 

In my signature is a link to my tutorial on using MIDI in Sonar I think it will help you sort this out. 

Thanks, Johnny. I'll check them out.
 
Edit: Johnny, I'm reading through your tutorial and following along in SPlat. Very Nice!
 
One question, though, when you mention inserting the Stereo Bus, my copy of SPlat doesn't do anything. And  yes, I looked all the way down at the bottom of the track view. Also, the console view doesn't show it, either -- which means it didn't load for some reason. I tried the Surround command also. Same difference. Now, I'm wondering why my copy of SPlat isn't loading these objects. Any idea why it isn't?
 

It is there,, it's a matter of finding the little line.  
Did you try Shift B? that is show hide buss pane.  
Roll your mouse pointer to the bottom of the Sonar window until you get a pointer icon the looks like a = with an arrow above and below. Left click and drag up. 
The other possibility is your graphics are out of wack and your not seeing the bottom of the Sonar window. 
 
But a bigger mystery is when you say it does not show in console view? For me it actually always plunks itself right in the middle. 
But it to can go off screen to the right and it's the same deal with the mouse pointer. 
The Buss Pane is a separate window from the track pane but the two are always connected.