Actually I just realized that selecting your clips before export will not affect the start/end point of the midi track. The exported midi track will automatically end after the last piece of midi info contained in your tracks. It doesn’t matter as long as the midi track is shorter or the same length as your audio. The cymatic will automatically make your song as long as the longest audio or midi file you loaded.
Beware that if you have any markers in your session the midi export will automatically make the file end at the marker. So either delete all your markers before export or place your marker right where you want the midi track to end. I had a marker sitting at 12 minutes in my pt session, and when I loaded my midi track onto the cymatic it made my 4 minute long song into a 12 minute with the last 6 minutes silent. I couldn’t figure out why until I realized PT had exported the midi file as 12 mins long.